Method and apparatus for decoding video according to individual parsing or decoding in data unit level, and method and apparatus for encoding video for individual parsing or decoding in data unit level

ABSTRACT

A video decoding method including: extracting, from a bitstream of an encoded video, at least one of information indicating independent parsing of a data unit and information indicating independent decoding of a data unit; extracting encoded video data and information about a coded depth and an encoding mode according to maximum coding units by parsing the bitstream based on the information indicating independent parsing of the data unit; and decoding at least one coding unit according to a coded depth of each maximum coding unit of the encoded video data, based on the information indicating independent decoding in the data unit and the information about the coded depth and the encoding mode according to maximum coding units.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority from Korean Patent Application No.10-2009-0101190, filed on Oct. 23, 2009 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

Apparatuses and methods consistent with exemplary embodiments relate toencoding and decoding a video.

2. Description of the Related Art

As hardware for reproducing and storing high resolution or high qualityvideo content is being developed and supplied, a need for a video codecfor effectively encoding or decoding the high resolution or high qualityvideo content is increasing. In a related art video codec, a video isencoded or decoded according to a limited encoding method based on amacroblock having a predetermined size. Macroblocks are sequentiallyencoded or decoded, and prediction encoding or decoding that refers tonearby information is widely used.

SUMMARY

One or more exemplary embodiments provide encoding a video according toan independent encoding in a predetermined data unit level, and decodinga video according to independent parsing or independent decoding in apredetermined data unit level.

According to an aspect of an exemplary embodiment, there is provided avideo decoding method including: extracting, from a bitstream of anencoded video, at least one of information indicating independentparsing of a data unit and information indicating independent decodingof a data unit; extracting encoded video data and information about acoded depth and an encoding mode according to maximum coding units byparsing the bitstream based on the information indicating independentparsing of the data unit; and decoding at least one coding unitaccording to a coded depth of each maximum coding unit of the encodedvideo data, based on the information indicating independent decoding ofthe data unit and the information about the coded depth and the encodingmode according to maximum coding units. The data unit includes one of agroup of at least one coding unit and a group of at least one maximumcoding unit.

The coding unit may be characterized by a maximum size and a depth.

The depth may denote a number of times a coding unit is hierarchicallysplit, and as the depth deepens, deeper coding units according to depthsmay be split from the maximum coding unit to obtain minimum codingunits, wherein the depth is deepened from an upper depth to a lowerdepth, wherein as the depth deepens, the number of times the maximumcoding unit is split increases, and a total number of possible times themaximum coding unit is split corresponds to a maximum depth, and whereinthe maximum size and a maximum depth of the coding unit may bepredetermined.

The information indicating independent parsing of the data unit mayinclude information indicating independent parsing in a coding unitlevel, which indicates whether it is possible to extract informationindependently encoded for each maximum coding unit from the bitstream,and the information indicating independent decoding of the data unit mayinclude information indicating independent decoding in a coding unitlevel, which indicates whether it is possible to decode dataindependently encoded for each maximum coding unit.

The information indicating independent parsing in the coding unit leveland the information indicating independent decoding in the coding unitlevel may be set independently from each other.

The decoding may include, if predetermined nearby information is notreferenceable to perform prediction decoding on the at least one codingunit because the predetermined nearby information is not decoded beforethe at least one coding unit, performing prediction encoding on the atleast one coding unit by searching for and referring to referenceablenearby information, according to the information indicating independentparsing of the data unit and the information indicating independentdecoding of the data unit.

The decoding may include, if only a partial region of the encoded videois to be decoded, decoding only at least one maximum coding unit of theencoded video data, which corresponds to the partial region, based onthe information indicating independent encoding in the coding unitlevel. Information indicating whether to perform partial region decodingon the data unit or information indicating target data unit of thepartial region decoding may be extracted from the bitstream.

The video decoding method may further include restoring and reproducingvideo data, which is decoded in parallel per a predetermined number ofcoding units in the coding unit level, in parallel in the coding unitlevel, based on the information indicating independent encoding in thecoding unit level.

The performing the prediction decoding may include, if current nearbyinformation of the at least one coding unit is not referenceable,decoding the at least one coding unit by using another piece ofcurrently referenceable nearby information by the at least one codingunit, or information about a current coding unit, so as to perform atleast one of intra prediction, inter prediction, frequency domainprediction decoding, entropy decoding according to context-basedadaptive binary arithmetic coding (CABAC), and a post process of intraprediction value on the at least one coding unit.

The information regarding the data unit indicating a size of the codingunit or the number of the group of at least one coding unit or thenumber of the group of at least one maximum coding unit may be extractedfrom the bitstream.

The information indicating independent parsing of the data unit or theinformation indicating independent decoding of the data unit may beextracted from a slice header of the bitstream or a sequence parameterset.

According to an aspect of another exemplary embodiment, there isprovided a video encoding method including: splitting a current pictureinto at least one maximum coding unit; determining an encoding depth anda coding unit corresponding to the encoding depth to output a result ofencoding video data of the at least one maximum coding unit based ondeeper coding units having a hierarchical structure, in which a codingunit of an upper depth is split as a depth deepens, according to atleast one split region of the at least one maximum coding unit; andoutputting a bitstream including video data encoded in the encodingdepth for each of the at least one maximum coding unit, informationabout a coded depth and an encoding mode according to the at least onemaximum coding unit, and at least one of information indicatingindependent parsing of a data unit and information indicatingindependent decoding of a data unit.

The outputting the bitstream may include setting the informationindicating independent decoding of the data unit based on whether thedata unit is independently encoded while encoding the video data todetermine the encoding depth.

The outputting the bitstream may include setting the informationindicating independent parsing of the data unit based on whether theencoded video data and the information about the coded depth and theencoding mode according to at least one maximum coding unit areindependently inserted into the bitstream for each data unit. Theinformation regarding the data unit indicating a size of the coding unitor the number of the group of at least one coding unit or the number ofthe group of at least one maximum coding unit may be inserted into thebitstream.

The determining the encoding depth and the coding unit may include, ifreference information used to perform prediction encoding on the codingunit is not information about a previous coding unit as the coding unitis independently encoded in the coding unit level, searching for andreferring to referenceable nearby information from among nearbyinformation encoded before the coding unit so as to predict the codingunit.

The searching for and referring to the nearby information may includereferring to nearby information that is encoded before a current codingunit from among the nearby information, or to information about thecurrent coding unit, when intra prediction, frequency domain predictionencoding, inter prediction, a post process after intra prediction, orentropy encoding according to CABAC is performed on the coding unit.

The video encoding method and the video decoding method may process thecoding units in parallel simultaneously per a plurality of coding unitsby using a plurality of independent processors.

According to an aspect of another exemplary embodiment, there isprovided a video decoding apparatus including: a receiver whichextracts, from a bitstream of an encoded video, at least one ofinformation indicating independent parsing of a data unit andinformation indicating independent decoding of a data unit; a parserwhich extracts encoded video data and information about a coded depthand an encoding mode according to maximum coding units by parsing thebitstream based on the information indicating independent parsing of thedata unit; and a decoder which decodes at least one coding unitaccording to coded depth of each maximum coding unit of the encodedvideo data, based on the information indicating independent decoding ofthe data unit and the information about the coded depth and the encodingmode according to maximum coding units.

According to an aspect of another exemplary embodiment, there isprovided a video encoding apparatus including: a maximum coding unitsplitter which splits a current picture into at least one maximum codingunit; a coding unit determiner which determines an encoding depth and acoding unit corresponding to the encoding depth to output a result ofencoding video data of the at least one maximum coding unit based ondeeper coding units having a hierarchical structure, in which a codingunit of an upper depth is split as a depth deepens, according to atleast one split region of the at least one maximum coding unit; and anoutput unit which outputs a bitstream including video data encoded inthe encoding depth for each of the at least one maximum coding unit,information about a coded depth and an encoding mode according to the atleast one maximum coding unit, and at least one of informationindicating independent parsing of a data unit and information indicatingindependent decoding of a data unit.

According to an aspect of another exemplary embodiment, there isprovided a video decoding method including: extracting, from abitstream, encoded video data and information about a coded depth and anencoding mode according to maximum coding units by parsing the bitstreambased on information indicating independent parsing of a data unit; anddecoding at least one coding unit according to a coded depth of eachmaximum coding unit of the encoded video data, based on informationindicating independent decoding of a data unit and the information aboutthe coded depth and the encoding mode according to maximum coding units.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon aprogram for executing the video decoding method.

According to an aspect of another exemplary embodiment, there isprovided a computer readable recording medium having recorded thereon aprogram for executing the video encoding method.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become more apparent by describingin detail exemplary embodiments thereof with reference to the attacheddrawings in which:

FIG. 1 is a block diagram of a video encoding apparatus, according to anexemplary embodiment;

FIG. 2 is a block diagram of a video decoding apparatus, according to anexemplary embodiment;

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment;

FIG. 4 is a block diagram of an image encoder based on coding unitsaccording to an exemplary embodiment;

FIG. 5 is a block diagram of an image decoder based on coding unitsaccording to an exemplary embodiment;

FIG. 6 is a diagram illustrating deeper coding units according to depthsand partitions according to an exemplary embodiment;

FIG. 7 is a diagram for describing a relationship between a coding unitand transformation units, according to an exemplary embodiment;

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment;

FIG. 9 is a diagram of deeper coding units according to depths,according to an exemplary embodiment;

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units, prediction units, and transformation units, according toone or more exemplary embodiments;

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information of exemplary Table 1 belowaccording to an exemplary embodiment;

FIG. 14 is a flowchart illustrating a video encoding method, accordingto an exemplary embodiment;

FIG. 15 is a flowchart illustrating a video decoding method, accordingto an exemplary embodiment;

FIG. 16 is a block diagram of a video encoding apparatus for independentparsing and independent decoding in a coding unit level, according to anexemplary embodiment;

FIG. 17 is a block diagram of a video decoding apparatus according toindependent parsing and independent decoding in a coding unit level,according to an exemplary embodiment;

FIG. 18 is an outline for describing a parallel process in a slice levelaccording to a H.264 standard encoding and decoding method;

FIG. 19 is a table showing possible combinations of a parallel processin a slice level, and a parallel process in a coding unit levelaccording to one or more exemplary embodiments;

FIG. 20 is a diagram for describing a parallel process in a coding unitlevel, according to an exemplary embodiment;

FIG. 21 is a diagram for describing a hierarchical parallel process in adata unit, according to an exemplary embodiment;

FIG. 22 is a diagram for describing possible partial decoding accordingto independent decoding in a coding unit level, according to anexemplary embodiment;

FIG. 23 is a diagram of a possible parallel display in a coding unitaccording to parallel decoding in a coding unit level, according to anexemplary embodiment;

FIG. 24 is a syntax of a sequence parameter set into which informationindicating independent parsing in a coding unit level and informationindicating independent decoding in a coding unit level are inserted,according to an exemplary embodiment;

FIG. 25 is a diagram for describing intra prediction for independentdecoding in a coding unit level, according to an exemplary embodiment;

FIG. 26 is a diagram for describing a post process of intra predictionusing a nearby restoration sample, according to an exemplary embodiment;

FIG. 27 is a diagram for describing a post process of intra predictionfor independent decoding in a coding unit level, according to anexemplary embodiment;

FIG. 28 is a diagram for describing entropy encoding and decodingcomplying with a context-adaptive binary arithmetic coding (CABAC)method, for independent decoding in a coding unit level according to anexemplary embodiment, and independent parsing in a coding unit levelaccording to an exemplary embodiment;

FIG. 29 is a flowchart illustrating a video encoding method forindependent parsing or independent decoding, according to an exemplaryembodiment; and

FIG. 30 is a flowchart illustrating a video decoding method according toindependent parsing or independent decoding, according to an exemplaryembodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the exemplary embodiments will be described more fully withreference to the accompanying drawings, in which exemplary embodimentsare shown. Furthermore, expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list. In the exemplaryembodiments, “unit” may or may not refer to a unit of size, depending onits context.

Hereinafter, a “coding unit” is an encoding data unit in which the imagedata is encoded at an encoder side and an encoded data unit in which theencoded image data is decoded at a decoder side, according to exemplaryembodiments. Also, a “coded depth” denotes a depth where a coding unitis encoded.

Hereinafter, an “image” may denote a still image for a video or a movingimage, that is, the video itself.

Video encoding and decoding in data units having a hierarchical treestructure according to exemplary embodiments will be described withreference to FIGS. 1 through 15. Video encoding and decoding consideringindependent parsing or independent decoding in a coding unit level basedon the coding units having a hierarchical tree structure according toexemplary embodiments will be described with reference to FIGS. 16through 30.

A video encoding apparatus, a video decoding apparatus, a video encodingmethod, and a video decoding method, according to exemplary embodiments,will now be described with reference to FIGS. 1 through 15.

FIG. 1 is a block diagram of a video encoding apparatus 100, accordingto an exemplary embodiment. Referring to FIG. 1, the video encodingapparatus 100 includes a maximum coding unit splitter 110, a coding unitdeterminer 120, and an output unit 130.

The maximum coding unit splitter 110 may split a current picture basedon a maximum coding unit for the current picture of an image. If thecurrent picture is larger than the maximum coding unit, image data ofthe current picture may be split into the at least one maximum codingunit. The maximum coding unit according to an exemplary embodiment maybe a data unit having a size of 32×32, 64×64, 128×128, 256×256, etc.,wherein a shape of the data unit is a square having a width and heightin squares of 2. The image data may be output to the coding unitdeterminer 120 according to the at least one maximum coding unit.

A coding unit according to an exemplary embodiment may be characterizedby a maximum size and a depth. The depth denotes a number of times thecoding unit is spatially split from the maximum coding unit, and as thedepth deepens or increases, deeper coding units according to depths maybe split from the maximum coding unit to a minimum coding unit. A depthof the maximum coding unit is an uppermost depth and a depth of theminimum coding unit is a lowermost depth. Since a size of a coding unitcorresponding to each depth decreases as the depth of the maximum codingunit deepens, a coding unit corresponding to an upper depth may includea plurality of coding units corresponding to lower depths.

As described above, the image data of the current picture is split intothe maximum coding units according to a maximum size of the coding unit,and each of the maximum coding units may include deeper coding unitsthat are split according to depths. Since the maximum coding unitaccording to an exemplary embodiment is split according to depths, theimage data of a spatial domain included in the maximum coding unit maybe hierarchically classified according to depths.

A maximum depth and a maximum size of a coding unit, which limit thetotal number of times a height and a width of the maximum coding unitare hierarchically split may be predetermined.

The coding unit determiner 120 encodes at least one split regionobtained by splitting a region of the maximum coding unit according todepths, and determines a depth to output an encoded image data accordingto the at least one split region. That is, the coding unit determiner120 determines a coded depth by encoding the image data in the deepercoding units according to depths, according to the maximum coding unitof the current picture, and selecting a depth having the least encodingerror. Thus, the encoded image data of the coding unit corresponding tothe determined coded depth is output to the output unit 130. Also, thecoding units corresponding to the coded depth may be regarded as encodedcoding units.

The determined coded depth and the encoded image data according to thedetermined coded depth are output to the output unit 130.

The image data in the maximum coding unit is encoded based on the deepercoding units corresponding to at least one depth equal to or below themaximum depth, and results of encoding the image data are compared basedon each of the deeper coding units. A depth having the least encodingerror may be selected after comparing encoding errors of the deepercoding units. At least one coded depth may be selected for each maximumcoding unit.

The size of the maximum coding unit is split as a coding unit ishierarchically split according to depths, and as the number of codingunits increases. Also, even if coding units correspond to a same depthin one maximum coding unit, it is determined whether to split each ofthe coding units corresponding to the same depth to a lower depth bymeasuring an encoding error of the image data of each coding unit,separately. Accordingly, even when image data is included in one maximumcoding unit, the image data is split to regions according to the depthsand the encoding errors may differ according to regions in the onemaximum coding unit, and thus the coded depths may differ according toregions in the image data. Therefore, one or more coded depths may bedetermined in one maximum coding unit, and the image data of the maximumcoding unit may be divided according to coding units of at least onecoded depth.

Accordingly, the coding unit determiner 120 may determine coding unitshaving a tree structure included in the maximum coding unit. The codingunits having a tree structure according to an exemplary embodimentinclude coding units corresponding to a depth determined to be the codeddepth, from among deeper coding units included in the maximum codingunit. A coding unit of a coded depth may be hierarchically determinedaccording to depths in the same region of the maximum coding unit, andmay be independently determined in different regions. Similarly, a codeddepth in a current region may be independently determined from a codeddepth in another region.

A maximum depth according to an exemplary embodiment is an index relatedto a number of splitting times from a maximum coding unit to a minimumcoding unit. A first maximum depth according to an exemplary embodimentmay denote a total number of splitting times from the maximum codingunit to the minimum coding unit. A second maximum depth according to anexemplary embodiment may denote a total number of depth levels from themaximum coding unit to the minimum coding unit. For example, when adepth of the maximum coding unit is 0, a depth of a coding unit in whichthe maximum coding unit is split once may be set to 1, and a depth of acoding unit in which the maximum coding unit is split twice may be setto 2. Here, if the minimum coding unit is a coding unit in which themaximum coding unit is split four times, 5 depth levels of depths 0, 1,2, 3 and 4 exist. Thus, the first maximum depth may be set to 4 and thesecond maximum depth may be set to 5.

Prediction encoding and transformation may be performed according to themaximum coding unit. The prediction encoding and the transformation arealso performed based on the deeper coding units according to a depthequal to or depths less than the maximum depth, based on the maximumcoding unit. Transformation may be performed according to a method oforthogonal transformation or integer transformation.

Since the number of deeper coding units increases whenever the maximumcoding unit is split according to depths, encoding such as theprediction encoding and the transformation is performed on all of thedeeper coding units generated as the depth deepens. For convenience ofdescription, the prediction encoding and the transformation willhereinafter be described based on a coding unit of a current depth, in amaximum coding unit.

The video encoding apparatus 100 may variably select at least one of asize and a shape of a data unit for encoding the image data. In order toencode the image data, operations, such as prediction encoding,transformation, and entropy encoding, may be performed, and at thistime, the same data unit may be used for all operations or differentdata units may be used for each operation.

For example, the video encoding apparatus 100 may select a coding unitfor encoding the image data and a data unit different from the codingunit so as to perform the prediction encoding on the image data in thecoding unit.

In order to perform prediction encoding in the maximum coding unit, theprediction encoding may be performed based on a coding unitcorresponding to a coded depth, i.e., based on a coding unit that is nolonger split to coding units corresponding to a lower depth.Hereinafter, the coding unit that is no longer split and becomes a basisunit for prediction encoding will be referred to as a prediction unit. Apartition obtained by splitting the prediction unit may include aprediction unit or a data unit obtained by splitting at least one of aheight and a width of the prediction unit.

For example, when a coding unit of 2N×2N (where N is a positive integer)is no longer split and becomes a prediction unit of 2N×2N, a size of apartition may be 2N×2N, 2N×N, N×2N, or N×N. Examples of a partition typeinclude symmetrical partitions that are obtained by symmetricallysplitting at least one of a height and a width of the prediction unit,partitions obtained by asymmetrically splitting the height or width ofthe prediction unit (such as 1:n or n:1), partitions that are obtainedby geometrically splitting the prediction unit, and partitions havingarbitrary shapes.

A prediction mode of the prediction unit may be at least one of an intramode, a inter mode, and a skip mode. For example, the intra mode or theinter mode may be performed on the partition of 2N×2N, 2N×N, N×2N, orN×N. In this case, the skip mode may be performed only on the partitionof 2N×2N. The encoding is independently performed on one prediction unitin a coding unit, thereby selecting a prediction mode having a leastencoding error.

The video encoding apparatus 100 may also perform the transformation onthe image data in a coding unit based on the coding unit for encodingthe image data and on a data unit that is different from the codingunit.

In order to perform the transformation in the coding unit, thetransformation may be performed based on a data unit having a sizesmaller than or equal to the coding unit. For example, the data unit forthe transformation may include a data unit for an intra mode and a dataunit for an inter mode.

A data unit used as a base of the transformation will hereinafter bereferred to as a transformation unit. A transformation depth indicatinga number of splitting times to reach the transformation unit bysplitting the height and the width of the coding unit may also be set inthe transformation unit. For example, in a current coding unit of 2N×2N,a transformation depth may be 0 when the size of a transformation unitis also 2N×2N, may be 1 when each of the height and width of the currentcoding unit is split into two equal parts, totally split into 4transformation units, and the size of the transformation unit is thusN×N, and may be 2 when each of the height and width of the currentcoding unit is split into four equal parts, totally split into 4²transformation units and the size of the transformation unit is thusN/2×N/2. For example, the transformation unit may be set according to ahierarchical tree structure, in which a transformation unit of an uppertransformation depth is split into four transformation units of a lowertransformation depth according to hierarchical characteristics of atransformation depth.

Similar to the coding unit, the transformation unit in the coding unitmay be recursively split into smaller sized regions, so that thetransformation unit may be determined independently in units of regions.Thus, residual data in the coding unit may be divided according to thetransformation having the tree structure according to transformationdepths.

Encoding information according to coding units corresponding to a codeddepth uses information about the coded depth and information related toprediction encoding and transformation. Accordingly, the coding unitdeterminer 120 determines a coded depth having a least encoding errorand determines a partition type in a prediction unit, a prediction modeaccording to prediction units, and a size of a transformation unit fortransformation.

Coding units according to a tree structure in a maximum coding unit anda method of determining a partition, according to exemplary embodiments,will be described in detail below with reference to FIGS. 3 through 12.

The coding unit determiner 120 may measure an encoding error of deepercoding units according to depths by using Rate-Distortion Optimizationbased on Lagrangian multipliers.

The output unit 130 outputs the image data of the maximum coding unit,which is encoded based on the at least one coded depth determined by thecoding unit determiner 120, and information about the encoding modeaccording to the coded depth, in bitstreams.

The encoded image data may be obtained by encoding residual data of animage.

The information about the encoding mode according to the coded depth mayinclude at least one of information about the coded depth, the partitiontype in the prediction unit, the prediction mode, and the size of thetransformation unit.

The information about the coded depth may be defined by using splitinformation according to depths, which indicates whether encoding isperformed on coding units of a lower depth instead of a current depth.If the current depth of the current coding unit is the coded depth,image data in the current coding unit is encoded and output. In thiscase, the split information may be defined to not split the currentcoding unit to a lower depth. Alternatively, if the current depth of thecurrent coding unit is not the coded depth, the encoding is performed onthe coding unit of the lower depth, and thus the split information maybe defined to split the current coding unit to obtain the coding unitsof the lower depth.

If the current depth is not the coded depth, encoding is performed onthe coding unit that is split into the coding unit of the lower depth.In this case, since at least one coding unit of the lower depth existsin one coding unit of the current depth, the encoding is repeatedlyperformed on each coding unit of the lower depth, and thus the encodingmay be recursively performed for the coding units having the same depth.

Since the coding units having a tree structure are determined for onemaximum coding unit, and information about at least one encoding mode isdetermined for a coding unit of a coded depth, information about atleast one encoding mode may be determined for one maximum coding unit.Also, a coded depth of the image data of the maximum coding unit may bedifferent according to locations since the image data is hierarchicallysplit according to depths, and thus information about the coded depthand the encoding mode may be set for the image data.

Accordingly, the output unit 130 may assign encoding information about acorresponding coded depth and an encoding mode to at least one of thecoding unit, the prediction unit, and a minimum unit included in themaximum coding unit.

The minimum unit according to an exemplary embodiment is a rectangulardata unit obtained by splitting the minimum coding unit of the lowermostdepth by 4. Alternatively, the minimum unit may be a maximum rectangulardata unit that may be included in all of the coding units, predictionunits, partition units, and transformation units included in the maximumcoding unit.

For example, the encoding information output through the output unit 130may be classified into encoding information according to coding units,and encoding information according to prediction units. The encodinginformation according to the coding units may include the informationabout the prediction mode and about the size of the partitions. Theencoding information according to the prediction units may includeinformation about an estimated direction of an inter mode, a referenceimage index of the inter mode, a motion vector, a chroma component of anintra mode, and an interpolation method of the intra mode. Also,information about a maximum size of the coding unit defined according topictures, slices, or GOPs, and information about a maximum depth may beinserted into at least one of a Sequence Parameter Set (SPS) and aheader of a bitstream.

In the video encoding apparatus 100, the deeper coding unit may be acoding unit obtained by dividing at least one of a height and a width ofa coding unit of an upper depth, which is one layer above, by two. Forexample, when the size of the coding unit of the current depth is 2N×2N,the size of the coding unit of the lower depth may be N×N. Also, thecoding unit of the current depth having the size of 2N×2N may include amaximum of 4 coding units of the lower depth.

Accordingly, the video encoding apparatus 100 may form the coding unitshaving the tree structure by determining coding units having an optimumshape and an optimum size for each maximum coding unit, based on thesize of the maximum coding unit and the maximum depth determinedconsidering characteristics of the current picture. Also, since encodingmay be performed on each maximum coding unit by using any one of variousprediction modes and transformations, an optimum encoding mode may bedetermined considering characteristics of the coding unit of variousimage sizes.

Thus, if an image having high resolution or a large amount of data isencoded in a related art macroblock, a number of macroblocks per pictureexcessively increases. Accordingly, a number of pieces of compressedinformation generated for each macroblock increases, and thus it isdifficult to transmit the compressed information and data compressionefficiency decreases. However, by using the video encoding apparatus 100according to an exemplary embodiment, image compression efficiency maybe increased since a coding unit is adjusted while consideringcharacteristics of an image and increasing a maximum size of a codingunit while considering a size of the image.

FIG. 2 is a block diagram of a video decoding apparatus 200, accordingto an exemplary embodiment. Referring to FIG. 2, the video decodingapparatus 200 includes a receiver 210, an image data and encodinginformation extractor 220, and an image data decoder 230. Definitions ofvarious terms, such as a coding unit, a depth, a prediction unit, and atransformation unit, and information about various encoding modes forvarious operations of the video decoding apparatus 200 are similar tothose described with reference to FIG. 1.

The receiver 210 receives and parses a bitstream of an encoded video.The image data and encoding information extractor 220 extracts encodedimage data for each coding unit from the parsed bitstream, wherein thecoding units have a tree structure according to each maximum codingunit, and outputs the extracted image data to the image data decoder230. The image data and encoding information extractor 220 may extractinformation about a maximum size of a coding unit of a current picture,from a header about the current picture or an SPS.

Also, the image data and encoding information extractor 220 extractsinformation about a coded depth and an encoding mode for the codingunits having a tree structure according to each maximum coding unit,from the parsed bitstream. The extracted information about the codeddepth and the encoding mode is output to the image data decoder 230.That is, the image data in a bit stream is split into the maximum codingunit so that the image data decoder 230 decodes the image data for eachmaximum coding unit.

The information about the coded depth and the encoding mode according tothe maximum coding unit may be set for information about at least onecoding unit corresponding to the coded depth, and information about anencoding mode may include information about at least one of a partitiontype of a corresponding coding unit corresponding to the coded depth, aprediction mode, and a size of a transformation unit. Also, splittinginformation according to depths may be extracted as the informationabout the coded depth.

The information about the coded depth and the encoding mode according toeach maximum coding unit extracted by the image data and encodinginformation extractor 220 is information about a coded depth and anencoding mode determined to generate a minimum encoding error when anencoder, such as a video encoding apparatus 100 according to anexemplary embodiment, repeatedly performs encoding for each deepercoding unit based on depths according to each maximum coding unit.Accordingly, the video decoding apparatus 200 may restore an image bydecoding the image data according to a coded depth and an encoding modethat generates the minimum encoding error.

Since encoding information about the coded depth and the encoding modemay be assigned to a predetermined data unit from among a correspondingcoding unit, a prediction unit, and a minimum unit, the image data andencoding information extractor 220 may extract the information about thecoded depth and the encoding mode according to the predetermined dataunits. The predetermined data units to which the same information aboutthe coded depth and the encoding mode is assigned may be the data unitsincluded in the same maximum coding unit.

The image data decoder 230 restores the current picture by decoding theimage data in each maximum coding unit based on the information aboutthe coded depth and the encoding mode according to the maximum codingunits. For example, the image data decoder 230 may decode the encodedimage data based on the extracted information about the partition type,the prediction mode, and the transformation unit for each coding unitfrom among the coding units having the tree structure included in eachmaximum coding unit. A decoding process may include a predictionincluding intra prediction and motion compensation, and an inversetransformation. Inverse transformation may be performed according to amethod of inverse orthogonal transformation or inverse integertransformation.

The image data decoder 230 may perform at least one of intra predictionand motion compensation according to a partition and a prediction modeof each coding unit, based on the information about the partition typeand the prediction mode of the prediction unit of the coding unitaccording to coded depths.

Also, the image data decoder 230 may perform inverse transformationaccording to each transformation unit in the coding unit, based on theinformation about the size of the transformation unit of the coding unitaccording to coded depths, so as to perform the inverse transformationaccording to maximum coding units.

The image data decoder 230 may determine at least one coded depth of acurrent maximum coding unit by using split information according todepths. If the split information indicates that image data is no longersplit in the current depth, the current depth is a coded depth.Accordingly, the image data decoder 230 may decode encoded data of atleast one coding unit corresponding to the each coded depth in thecurrent maximum coding unit by using at least one of the informationabout the partition type of the prediction unit, the prediction mode,and the size of the transformation unit for each coding unitcorresponding to the coded depth, and output the image data of thecurrent maximum coding unit.

For example, data units including the encoding information having thesame split information may be gathered by observing the encodinginformation set assigned for the predetermined data unit from among thecoding unit, the prediction unit, and the minimum unit, and the gathereddata units may be considered to be one data unit to be decoded by theimage data decoder 230 in the same encoding mode.

The video decoding apparatus 200 may obtain information about at leastone coding unit that generates the minimum encoding error when encodingis recursively performed for each maximum coding unit, and may use theinformation to decode the current picture. That is, the coding unitshaving the tree structure determined to be the optimum coding units ineach maximum coding unit may be decoded. Also, the maximum size of thecoding unit may be determined considering at least one of resolution andan amount of image data.

Accordingly, even if image data has high resolution and a large amountof data, the image data may be efficiently decoded and restored by usinga size of a coding unit and an encoding mode, which are adaptivelydetermined according to characteristics of the image data, andinformation about an optimum encoding mode received from an encoder.

A method of determining coding units having a tree structure, aprediction unit, and a transformation unit, according to one or moreexemplary embodiments, will now be described with reference to FIGS. 3through 13.

FIG. 3 is a diagram for describing a concept of coding units accordingto an exemplary embodiment. A size of a coding unit may be expressed inwidth×height. For example, the size of the coding unit may be 64×64,32×32, 16×16, or 8×8. A coding unit of 64×64 may be split intopartitions of 64×64, 64×32, 32×64, or 32×32, and a coding unit of 32×32may be split into partitions of 32×32, 32×16, 16×32, or 16×16, a codingunit of 16×16 may be split into partitions of 16×16, 16×8, 8×16, or 8×8,and a coding unit of 8×8 may be split into partitions of 8×8, 8×4, 4×8,or 4×4.

Referring to FIG. 3, there is exemplarily provided first video data 310with a resolution of 1920×1080 and a coding unit with a maximum size of64 a maximum depth of 2. Furthermore, there is exemplarily providedsecond video data 320 with a resolution of 1920×1080 and a coding unitwith a maximum size of 64 and a maximum depth of 3. Also, there isexemplarily provided third video data 330 with a resolution of 352×288and a coding unit having a maximum size of 16 and a maximum depth of 1.The maximum depth shown in FIG. 3 denotes a total number of splits froma maximum coding unit to a minimum decoding unit.

If a resolution is high or a data amount is large, a maximum size of acoding unit may be large so as to increase encoding efficiency and toaccurately reflect characteristics of an image. Accordingly, the maximumsize of the coding unit of the first and second video data 310 and 320having the higher resolution than the third video data 330 may be 64.

Since the maximum depth of the first video data 310 is 2, coding units315 of the first video data 310 may include a maximum coding unit havinga long axis size of 64, and coding units having long axis sizes of 32and 16 since depths are deepened to two layers by splitting the maximumcoding unit twice. Meanwhile, since the maximum depth of the third videodata 330 is 1, coding units 335 of the third video data 330 may includea maximum coding unit having a long axis size of 16, and coding unitshaving a long axis size of 8 since depths are deepened to one layer bysplitting the maximum coding unit once.

Since the maximum depth of the second video data 320 is 3, coding units325 of the second video data 320 may include a maximum coding unithaving a long axis size of 64, and coding units having long axis sizesof 32, 16, and 8 since the depths are deepened to 3 layers by splittingthe maximum coding unit three times. As a depth deepens, detailedinformation may be precisely expressed.

FIG. 4 is a block diagram of an image encoder 400 based on coding units,according to an exemplary embodiment. The image encoder 400 may performoperations of a coding unit determiner 120 of a video encoding apparatus100 according to an exemplary embodiment to encode image data. That is,referring to FIG. 4, an intra predictor 410 performs intra prediction oncoding units, from among a current frame 405, in an intra mode, and amotion estimator 420 and a motion compensator 425 perform interestimation and motion compensation on coding units, from among thecurrent frame 405, in an inter mode by using the current frame 405 and areference frame 495.

Data output from the intra predictor 410, the motion estimator 420, andthe motion compensator 425 is output as a quantized transformationcoefficient through a transformer 430 and a quantizer 440. The quantizedtransformation coefficient is restored as data in a spatial domainthrough an inverse quantizer 460 and an inverse transformer 470, and therestored data in the spatial domain is output as the reference frame 495after being post-processed through a deblocking unit 480 and a loopfiltering unit 490. The quantized transformation coefficient may beoutput as a bitstream 455 through an entropy encoder 450.

In order for the image encoder 400 to be applied in the video encodingapparatus 100, elements of the image encoder 400, i.e., the intrapredictor 410, the motion estimator 420, the motion compensator 425, thetransformer 430, the quantizer 440, the entropy encoder 450, the inversequantizer 460, the inverse transformer 470, the deblocking unit 480, andthe loop filtering unit 490, perform operations based on each codingunit from among coding units having a tree structure while consideringthe maximum depth of each maximum coding unit.

Specifically, the intra predictor 410, the motion estimator 420, and themotion compensator 425 determine partitions and a prediction mode ofeach coding unit from among the coding units having a tree structurewhile considering a maximum size and a maximum depth of a currentmaximum coding unit, and the transformer 430 determines the size of thetransformation unit in each coding unit from among the coding unitshaving a tree structure.

FIG. 5 is a block diagram of an image decoder 500 based on coding units,according to an exemplary embodiment. Referring to FIG. 5, a parser 510parses encoded image data to be decoded and information about encodingused for decoding from a bitstream 505. The encoded image data is outputas inverse quantized data through an entropy decoder 520 and an inversequantizer 530, and the inverse quantized data is restored to image datain a spatial domain through an inverse transformer 540.

An intra predictor 550 performs intra prediction on coding units in anintra mode with respect to the image data in the spatial domain, and amotion compensator 560 performs motion compensation on coding units inan inter mode by using a reference frame 585.

The image data in the spatial domain, which passed through the intrapredictor 550 and the motion compensator 560, may be output as arestored frame 595 after being post-processed through a deblocking unit570 and a loop filtering unit 580. Also, the image data that ispost-processed through the deblocking unit 570 and the loop filteringunit 580 may be output as the reference frame 585.

In order to decode the image data in an image data decoder 230 of avideo decoding apparatus 200 according to an exemplary embodiment, theimage decoder 500 may perform operations that are performed after theparser 510. In order for the image decoder 500 to be applied in thevideo decoding apparatus 200, elements of the image decoder 500, i.e.,the parser 510, the entropy decoder 520, the inverse quantizer 530, theinverse transformer 540, the intra predictor 550, the motion compensator560, the deblocking unit 570, and the loop filtering unit 580, performoperations based on coding units having a tree structure for eachmaximum coding unit.

Specifically, the intra predictor 550 and the motion compensator 560perform operations based on partitions and a prediction mode for each ofthe coding units having a tree structure, and the inverse transformer540 performs operations based on a size of a transformation unit foreach coding unit.

FIG. 6 is a diagram illustrating deeper coding units according todepths, and partitions, according to an exemplary embodiment.

A video encoding apparatus 100 and a video decoding apparatus 200 usehierarchical coding units so as to consider characteristics of an image.A maximum height, a maximum width, and a maximum depth of coding unitsmay be adaptively determined according to the characteristics of theimage, or may be differently set by a user. Sizes of deeper coding unitsaccording to depths may be determined according to the predeterminedmaximum size of the coding unit.

Referring to FIG. 6, in a hierarchical structure 600 of coding unitsaccording to an exemplary embodiment, the maximum height and the maximumwidth of the coding units are each 64, and the maximum depth is 4. Sincea depth deepens along a vertical axis of the hierarchical structure 600,a height and a width of a deeper coding unit are each split. Also, aprediction unit and partitions, which are bases for prediction encodingof each deeper coding unit, are shown along a horizontal axis of thehierarchical structure 600.

That is, a first coding unit 610 is a maximum coding unit in thehierarchical structure 600, wherein a depth is 0 and a size, i.e., aheight by width, is 64×64. The depth deepens along the vertical axis,and a second coding unit 620 having a size of 32×32 and a depth of 1, athird coding unit 630 having a size of 16×16 and a depth of 2, a fourthcoding unit 640 having a size of 8×8 and a depth of 3, and a fifthcoding unit 650 having a size of 4×4 and a depth of 4 exist. The fifthcoding unit 650 having the size of 4×4 and the depth of 4 is a minimumcoding unit.

The prediction unit and the partitions of a coding unit are arrangedalong the horizontal axis according to each depth. That is, if the firstcoding unit 610 having the size of 64×64 and the depth of 0 is aprediction unit, the prediction unit may be split into partitionsincluded in the first coding unit 610, i.e., a partition 610 having asize of 64×64, partitions 612 having a size of 64×32, partitions 614having a size of 32×64, or partitions 616 having a size of 32×32.

Similarly, a prediction unit of the second coding unit 620 having thesize of 32×32 and the depth of 1 may be split into partitions includedin the second coding unit 620, i.e., a partition 620 having a size of32×32, partitions 622 having a size of 32×16, partitions 624 having asize of 16×32, and partitions 626 having a size of 16×16.

Similarly, a prediction unit of the third coding unit 630 having thesize of 16×16 and the depth of 2 may be split into partitions includedin the third coding unit 630, i.e., a partition having a size of 16×16included in the third coding unit 630, partitions 632 having a size of16×8, partitions 634 having a size of 8×16, and partitions 636 having asize of 8×8.

Similarly, a prediction unit of the fourth coding unit 640 having thesize of 8×8 and the depth of 3 may be split into partitions included inthe fourth coding unit 640, i.e. a partition having a size of 8×8included in the fourth coding unit 640, partitions 642 having a size of8×4, partitions 644 having a size of 4×8, and partitions 646 having asize of 4×4.

The fifth coding unit 650 having the size of 4×4 and the depth of 4 isthe minimum coding unit and a coding unit of the lowermost depth. Aprediction unit of the fifth coding unit 650 is only assigned to apartition having a size of 4×4.

In order to determine the at least one coded depth of the coding unitsof the maximum coding unit 610, a coding unit determiner 120 of thevideo encoding apparatus 100 performs encoding for coding unitscorresponding to each depth included in the maximum coding unit 610.

A number of deeper coding units according to depths including data inthe same range and the same size increases as the depth deepens. Forexample, four coding units corresponding to a depth of 2 are used tocover data that is included in one coding unit corresponding to a depthof 1. Accordingly, in order to compare encoding results of the same dataaccording to depths, the coding unit corresponding to the depth of 1 andfour coding units corresponding to the depth of 2 are each encoded.

In order to perform encoding for a current depth from among the depths,a least encoding error may be selected for the current depth byperforming encoding for each prediction unit in the coding unitscorresponding to the current depth, along the horizontal axis of thehierarchical structure 600. Alternatively, the minimum encoding errormay be searched for by comparing the least encoding errors according todepths, by performing encoding for each depth as the depth deepens alongthe vertical axis of the hierarchical structure 600. A depth and apartition having the minimum encoding error in the first coding unit 610may be selected as the coded depth and a partition type of the firstcoding unit 610.

FIG. 7 is a diagram for describing a relationship between a coding unit710 and transformation units 720, according to an exemplary embodiment.

A video encoding or decoding apparatus 100 or 200 according to exemplaryembodiments encodes or decodes an image according to coding units havingsizes smaller than or equal to a maximum coding unit for each maximumcoding unit. Sizes of transformation units for transformation duringencoding may be selected based on data units that are not larger than acorresponding coding unit.

For example, in the video encoding or decoding apparatus 100 or 200, ifa size of the coding unit 710 is 64×64, transformation may be performedby using the transformation units 720 having a size of 32×32.

Also, data of the coding unit 710 having the size of 64×64 may beencoded by performing the transformation on each of the transformationunits having the size of 32×32, 16×16, 8×8, and 4×4, which are smallerthan 64×64, such that a transformation unit having the least codingerror may be selected.

FIG. 8 is a diagram for describing encoding information of coding unitscorresponding to a coded depth, according to an exemplary embodiment.Referring to FIG. 8, an output unit 130 of a video encoding apparatus100 according to an exemplary embodiment may encode and transmitinformation 800 about a partition type, information 810 about aprediction mode, and information 820 about a size of a transformationunit for each coding unit corresponding to a coded depth, as informationabout an encoding mode.

The information 800 about the partition type is information about ashape of a partition obtained by splitting a prediction unit of acurrent coding unit, wherein the partition is a data unit for predictionencoding the current coding unit. For example, a current coding unit CU0 having a size of 2N×2N may be split into any one of a partition 802having a size of 2N×2N, a partition 804 having a size of 2N×N, apartition 806 having a size of N×2N, and a partition 808 having a sizeof N×N. Here, the information 800 about the partition type is set toindicate one of the partition 804 having a size of 2N×N, the partition806 having a size of N×2N, and the partition 808 having a size of N×N

The information 810 about the prediction mode indicates a predictionmode of each partition. For example, the information 810 about theprediction mode may indicate a mode of prediction encoding performed ona partition indicated by the information 800 about the partition type,i.e., an intra mode 812, an inter mode 814, or a skip mode 816.

The information 820 about the size of a transformation unit indicates atransformation unit to be based on when transformation is performed on acurrent coding unit. For example, the transformation unit may be a firstintra transformation unit 822, a second intra transformation unit 824, afirst inter transformation unit 826, or a second intra transformationunit 828.

An image data and encoding information extractor 220 of a video decodingapparatus 200 according to an exemplary embodiment may extract and usethe information 800, 810, and 820 for decoding, according to each deepercoding unit FIG. 9 is a diagram of deeper coding units according todepths, according to an exemplary embodiment.

Split information may be used to indicate a change of a depth. The splitinformation indicates whether a coding unit of a current depth is splitinto coding units of a lower depth.

Referring to FIG. 9, a prediction unit 910 for prediction encoding acoding unit 900 having a depth of 0 and a size of 2N_(—)0×2N_(—)0 mayinclude partitions of a partition type 912 having a size of2N_(—)0×2N_(—)0, a partition type 914 having a size of 2N_(—)0×N_(—)0, apartition type 916 having a size of N_(—)0×2N_(—)0, and a partition type918 having a size of N_(—)0×N_(—)0. Though FIG. 9 only illustrates thepartition types 912 through 918 which are obtained by symmetricallysplitting the prediction unit 910, it is understood that a partitiontype is not limited thereto. For example, according to another exemplaryembodiment, the partitions of the prediction unit 910 may includeasymmetrical partitions, partitions having a predetermined shape, andpartitions having a geometrical shape.

Prediction encoding is repeatedly performed on one partition having asize of 2N_(—)0×2N_(—)0, two partitions having a size of 2N_(—)0×N_(—)0,two partitions having a size of N_(—)0×2N_(—)0, and four partitionshaving a size of N_(—)0×N_(—)0, according to each partition type. Theprediction encoding in an intra mode and an inter mode may be performedon the partitions having the sizes of 2N_(—)0×2N_(—)0, N_(—)0×2N_(—)0,2N_(—)0×N_(—)0, and N_(—)0×N_(—)0. The prediction encoding in a skipmode is performed only on the partition having the size of2N_(—)0×2N_(—)0.

Errors of encoding including the prediction encoding in the partitiontypes 912 through 918 are compared, and the least encoding error isdetermined among the partition types. If an encoding error is smallestin one of the partition types 912 through 916, the prediction unit 910may not be split into a lower depth.

For example, if the encoding error is the smallest in the partition type918, a depth is changed from 0 to 1 to split the partition type 918 inoperation 920, and encoding is repeatedly performed on coding units 930having a depth of 2 and a size of N_(—)0×N_(—)0 to search for a minimumencoding error.

A prediction unit 940 for prediction encoding the coding unit 930 havinga depth of 1 and a size of 2N_(—)1×2N_(—)1 (=N_(—)0×N_(—)0) may includepartitions of a partition type 942 having a size of 2N_(—)1×2N_(—)1, apartition type 944 having a size of 2N_(—)1×N_(—)1, a partition type 946having a size of N_(—)1×2N_(—)1, and a partition type 948 having a sizeof N_(—)1×N_(—)1.

As an example, if an encoding error is the smallest in the partitiontype 948, a depth is changed from 1 to 2 to split the partition type 948in operation 950, and encoding is repeatedly performed on coding units960, which have a depth of 2 and a size of N_(—)2×N_(—)2 to search for aminimum encoding error.

When a maximum depth is d, split operations according to each depth maybe performed up to when a depth becomes d−1, and split information maybe encoded as up to when a depth is one of 0 to d−2. For example, whenencoding is performed up to when the depth is d−1 after a coding unitcorresponding to a depth of d−2 is split in operation 970, a predictionunit 990 for prediction encoding a coding unit 980 having a depth of d−1and a size of 2N_(d−1)×2N_(d−1) may include partitions of a partitiontype 992 having a size of 2N_(d−1)×2N_(d−1), a partition type 994 havinga size of 2N_(d−1)×N_(d−1), a partition type 996 having a size ofN_(d−1)×2N_(d−1), and a partition type 998 having a size ofN_(d−1)×N_(d−1).

Prediction encoding may be repeatedly performed on one partition havinga size of 2N_(d−1)×2N_(d−1), two partitions having a size of2N_(d−1)×N_(d−1), two partitions having a size of N_(d−1)×2N_(d−1), fourpartitions having a size of N_(d−1)×N_(d−1) from among the partitiontypes 992 through 998 to search for a partition type having a minimumencoding error.

Even when the partition type 998 has the minimum encoding error, since amaximum depth is d, a coding unit CU_(d−1) having a depth of d−1 is nolonger split to a lower depth. In this case, a coded depth for thecoding units of a current maximum coding unit 900 is determined to bed−1 and a partition type of the current maximum coding unit 900 may bedetermined to be N_(d−1)×N_(d−1). Also, since the maximum depth is d anda minimum coding unit 980 having a lowermost depth of d−1 is no longersplit to a lower depth, split information for the minimum coding unit980 is not set.

A data unit 999 may be a minimum unit for the current maximum codingunit. A minimum unit according to an exemplary embodiment may be arectangular data unit obtained by splitting a minimum coding unit 980 by4. By performing the encoding repeatedly, a video encoding apparatus 100according to an exemplary embodiment may select a depth having the leastencoding error by comparing encoding errors according to depths of thecoding unit 900 to determine a coded depth, and set a correspondingpartition type and a prediction mode as an encoding mode of the codeddepth.

As such, the minimum encoding errors according to depths are compared inall of the depths of 1 through d, and a depth having the least encodingerror may be determined as a coded depth. The coded depth, the partitiontype of the prediction unit, and the prediction mode may be encoded andtransmitted as information about an encoding mode. Also, since a codingunit is split from a depth of 0 to a coded depth, split information ofthe coded depth is set to 0, and split information of depths excludingthe coded depth is set to 1.

An image data and encoding information extractor 220 of a video decodingapparatus 200 according to an exemplary embodiment may extract and usethe information about the coded depth and the prediction unit of thecoding unit 900 to decode the partition 912. The video decodingapparatus 200 may determine a depth, in which split information is 0, asa coded depth by using split information according to depths, and useinformation about an encoding mode of the corresponding depth fordecoding.

FIGS. 10 through 12 are diagrams for describing a relationship betweencoding units 1010, prediction units 1060, and transformation units 1070,according to one or more exemplary embodiments.

Referring to FIG. 10, the coding units 1010 are coding units having atree structure, corresponding to coded depths determined by a videoencoding apparatus 100 according to an exemplary embodiment, in amaximum coding unit. Referring to FIGS. 11 and 12, the prediction units1060 are partitions of prediction units of each of the coding units1010, and the transformation units 1070 are transformation units of eachof the coding units 1010.

When a depth of a maximum coding unit is 0 in the coding units 1010,depths of coding units 1012 and 1054 are 1, depths of coding units 1014,1016, 1018, 1028, 1050, and 1052 are 2, depths of coding units 1020,1022, 1024, 1026, 1030, 1032, and 1048 are 3, and depths of coding units1040, 1042, 1044, and 1046 are 4.

In the prediction units 1060, some coding units 1014, 1016, 1022, 1032,1048, 1050, 1052, and 1054 are obtained by splitting coding units of thecoding units 1010. In particular, partition types in the coding units1014, 1022, 1050, and 1054 have a size of 2N×N, partition types in thecoding units 1016, 1048, and 1052 have a size of N×2N, and a partitiontype of the coding unit 1032 has a size of N×N. Prediction units andpartitions of the coding units 1010 are smaller than or equal to eachcoding unit.

Transformation or inverse transformation is performed on image data ofthe coding unit 1052 in the transformation units 1070 in a data unitthat is smaller than the coding unit 1052. Also, the coding units 1014,1016, 1022, 1032, 1048, 1050, and 1052 of the transformation units 1070are different from those of the prediction units 1060 in terms of sizesand shapes. In other words, video encoding and decoding apparatuses 100and 200 according to exemplary embodiments may perform intra prediction,motion estimation, motion compensation, transformation, and inversetransformation individually on a data unit in the same coding unit.

Accordingly, encoding is recursively performed on each of coding unitshaving a hierarchical structure in each region of a maximum coding unitto determine an optimum coding unit, and thus coding units having arecursive tree structure may be obtained. Encoding information mayinclude split information about a coding unit, information about apartition type, information about a prediction mode, and informationabout a size of a transformation unit. Exemplary Table 1 shows theencoding information that may be set by the video encoding and decodingapparatuses 100 and 200.

TABLE 1 Split Information 0 (Encoding on Coding Unit having Size of 2N ×2N and Current Depth of d) Split Information 1 Prediction Mode PartitionType Size of Transformation Unit Repeatedly Intra SymmetricalAsymmetrical Split Information 0 Split Information 1 Encode InterPartition Partition of Transformation of Transformation Coding Skip(Only Type Type Unit Unit Units 2N × 2N) 2N × 2N 2N × nU 2N × 2N N × Nhaving 2N × N 2N × nD (Symmetrical Lower N × 2N nL × 2N Type) Depth of N× N nR × 2N N/2 × N/2 d + 1 (Asymmetrical Type)

An output unit 130 of the video encoding apparatus 100 may output theencoding information about the coding units having a tree structure, andan image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract the encoding information about thecoding units having a tree structure from a received bitstream.

Split information indicates whether a current coding unit is split intocoding units of a lower depth. If split information of a current depth dis 0, a depth in which a current coding unit is no longer split into alower depth is a coded depth. Information about a partition type,prediction mode, and a size of a transformation unit may be defined forthe coded depth. If the current coding unit is further split accordingto the split information, encoding is independently performed on splitcoding units of a lower depth.

A prediction mode may be one of an intra mode, an inter mode, and a skipmode. The intra mode and the inter mode may be defined in all partitiontypes, and the skip mode may be defined in only a partition type havinga size of 2N×2N.

The information about the partition type may indicate symmetricalpartition types having sizes of 2N×2N, 2N×N, N×2N, and N×N, which areobtained by symmetrically splitting a height or a width of a predictionunit, and asymmetrical partition types having sizes of 2N×nU, 2N×nD,nL×2N, and nR×2N, which are obtained by asymmetrically splitting theheight or the width of the prediction unit. The asymmetrical partitiontypes having the sizes of 2N×nU and 2N×nD may be respectively obtainedby splitting the height of the prediction unit in ratios of 1:3 and 3:1,and the asymmetrical partition types having the sizes of nL×2N and nR×2Nmay be respectively obtained by splitting the width of the predictionunit in ratios of 1:3 and 3:1

The size of the transformation unit may be set to be two types in theintra mode and two types in the inter mode. For example, if splitinformation of the transformation unit is 0, the size of thetransformation unit may be 2N×2N, which is the size of the currentcoding unit. If split information of the transformation unit is 1, thetransformation units may be obtained by splitting the current codingunit. Also, if a partition type of the current coding unit having thesize of 2N×2N is a symmetrical partition type, a size of atransformation unit may be N×N, and if the partition type of the currentcoding unit is an asymmetrical partition type, the size of thetransformation unit may be N/2×N/2.

The encoding information about coding units having a tree structure mayinclude at least one of a coding unit corresponding to a coded depth, acoding unit corresponding to a prediction unit, and a coding unitcorresponding to a minimum unit. The coding unit corresponding to thecoded depth may include at least one of a prediction unit and a minimumunit including the same encoding information.

Accordingly, it is determined whether adjacent data units are includedin the same coding unit corresponding to the coded depth by comparingencoding information of the adjacent data units. Also, a correspondingcoding unit corresponding to a coded depth is determined by usingencoding information of a data unit, and thus a distribution of codeddepths in a maximum coding unit may be determined.

Accordingly, if a current coding unit is predicted based on encodinginformation of adjacent data units, encoding information of data unitsin deeper coding units adjacent to the current coding unit may bedirectly referred to and used. However, it is understood that anotherexemplary embodiment is not limited thereto. For example, according toanother exemplary embodiment, if a current coding unit is predictedbased on encoding information of adjacent data units, data unitsadjacent to the current coding unit are searched using encodedinformation of the data units, and the searched adjacent coding unitsmay be referred for predicting the current coding unit.

FIG. 13 is a diagram for describing a relationship between a codingunit, a prediction unit or a partition, and a transformation unit,according to encoding mode information of exemplary Table 1, accordingto an exemplary embodiment.

Referring to FIG. 13, a maximum coding unit 1300 includes coding units1302, 1304, 1306, 1312, 1314, 1316, and 1318 of coded depths. Here,since the coding unit 1318 is a coding unit of a coded depth, splitinformation may be set to 0. Information about a partition type of thecoding unit 1318 having a size of 2N×2N may be set to be one of apartition type 1322 having a size of 2N×2N, a partition type 1324 havinga size of 2N×N, a partition type 1326 having a size of N×2N, a partitiontype 1328 having a size of N×N, a partition type 1332 having a size of2N×nU, a partition type 1334 having a size of 2N×nD, a partition type1336 having a size of nL×2N, and a partition type 1338 having a size ofnR×2N.

When the partition type is set to be symmetrical, i.e., the partitiontype 1322, 1324, 1326, or 1328, a transformation unit 1342 having a sizeof 2N×2N is set if split information (TU size flag) of a transformationunit is 0, and a transformation unit 1344 having a size of N×N is set ifa TU size flag is 1.

When the partition type is set to be asymmetrical, i.e., the partitiontype 1332, 1334, 1336, or 1338, a transformation unit 1352 having a sizeof 2N×2N is set if a TU size flag is 0, and a transformation unit 1354having a size of N/2×N/2 is set if a TU size flag is 1.

Referring to FIG. 13, the TU size flag is a flag having a value or 0 or1, though it is understood that the TU size flag is not limited to 1bit, and a transformation unit may be hierarchically split having a treestructure while the TU size flag increases from 0.

In this case, the size of a transformation unit that has been actuallyused may be expressed by using a TU size flag of a transformation unit,according to an exemplary embodiment, together with a maximum size andminimum size of the transformation unit. According to an exemplaryembodiment, a video encoding apparatus 100 is capable of encodingmaximum transformation unit size information, minimum transformationunit size information, and a maximum TU size flag. The result ofencoding the maximum transformation unit size information, the minimumtransformation unit size information, and the maximum TU size flag maybe inserted into an SPS. According to an exemplary embodiment, a videodecoding apparatus 200 may decode video by using the maximumtransformation unit size information, the minimum transformation unitsize information, and the maximum TU size flag.

For example, if the size of a current coding unit is 64×64 and a maximumtransformation unit size is 32×32, the size of a transformation unit maybe 32×32 when a TU size flag is 0, may be 16×16 when the TU size flag is1, and may be 8×8 when the TU size flag is 2.

As another example, if the size of the current coding unit is 32×32 anda minimum transformation unit size is 32×32, the size of thetransformation unit may be 32×32 when the TU size flag is 0. Here, theTU size flag cannot be set to a value other than 0, since the size ofthe transformation unit cannot be less than 32×32.

As another example, if the size of the current coding unit is 64×64 anda maximum TU size flag is 1, the TU size flag may be 0 or 1. Here, theTU size flag cannot be set to a value other than 0 or 1.

Thus, if it is defined that the maximum TU size flag isMaxTransformSizeIndex, a minimum transformation unit size isMinTransformSize, and a transformation unit size is RootTuSize when theTU size flag is 0, a current minimum transformation unit sizeCurrMinTuSize that can be determined in a current coding unit, may bedefined by Equation (1):

CurrMinTuSize=max(MinTransformSize,RootTuSize/(2̂MaxTransformSizeIndex))  (1).

Compared to the current minimum transformation unit size CurrMinTuSizethat can be determined in the current coding unit, a transformation unitsize RootTuSize when the TU size flag is 0 may denote a maximumtransformation unit size that can be selected in the system. In Equation(1), RootTuSize/(2̂MaxTransformSizeIndex) denotes a transformation unitsize when the transformation unit size RootTuSize, when the TU size flagis 0, is split a number of times corresponding to the maximum TU sizeflag. Furthermore, MinTransformSize denotes a minimum transformationsize. Thus, a smaller value from amongRootTuSize/(2̂MaxTransformSizeIndex) and MinTransformSize may be thecurrent minimum transformation unit size CurrMinTuSize that can bedetermined in the current coding unit.

According to an exemplary embodiment, the maximum transformation unitsize RootTuSize may vary according to the type of a prediction mode.

For example, if a current prediction mode is an inter mode, thenRootTuSize may be determined by using Equation (2) below. In Equation(2), MaxTransformSize denotes a maximum transformation unit size, andPUSize denotes a current prediction unit size.

RootTuSize=min(MaxTransformSize, PUSize) (2).

That is, if the current prediction mode is the inter mode, thetransformation unit size RootTuSize when the TU size flag is 0, may be asmaller value from among the maximum transformation unit size and thecurrent prediction unit size.

If a prediction mode of a current partition unit is an intra mode,RootTuSize may be determined by using Equation (3) below. In Equation(3), PartitionSize denotes the size of the current partition unit.

RootTuSize=min(MaxTransformSize, PartitionSize)  (3).

That is, if the current prediction mode is the intra mode, thetransformation unit size RootTuSize when the TU size flag is 0 may be asmaller value from among the maximum transformation unit size and thesize of the current partition unit.

However, the current maximum transformation unit size RootTuSize thatvaries according to the type of a prediction mode in a partition unit ismerely exemplary, and is not limited thereto in another exemplaryembodiment.

FIG. 14 is a flowchart illustrating a method of encoding a video,according to an exemplary embodiment. Referring to FIG. 14, in operation1210, a current picture is split into at least one maximum coding unit.A maximum depth indicating a total number of possible splitting timesmay be predetermined.

In operation 1220, a coded depth to output a final encoding resultaccording to at least one split region, which is obtained by splitting aregion of each maximum coding unit according to depths, is determined byencoding the at least one split region, and a coding unit according to atree structure is determined.

The maximum coding unit is spatially split whenever the depth deepens,and thus is split into coding units of a lower depth. Each coding unitmay be split into coding units of another lower depth by being spatiallysplit independently from adjacent coding units. Encoding is repeatedlyperformed on each coding unit according to depths.

Also, a transformation unit according to partition types having theleast encoding error is determined for each deeper coding unit. In orderto determine a coded depth having a minimum encoding error in eachmaximum coding unit, encoding errors may be measured and compared in alldeeper coding units according to depths.

In operation 1230, encoded image data that is the final encoding resultaccording to the coded depth is output for each maximum coding unit,with encoding information about the coded depth and an encoding mode.The information about the encoding mode may include at least one ofinformation about a coded depth or split information, information abouta partition type of a prediction unit, a prediction mode, and a size ofa transformation unit. The encoded information about the encoding modemay be transmitted to a decoder with the encoded image data.

FIG. 15 is a flowchart illustrating a method of decoding a video,according to an exemplary embodiment. Referring to FIG. 15, in operation1310, a bitstream of an encoded video is received and parsed.

In operation 1320, encoded image data of a current picture assigned to amaximum coding unit and information about a coded depth and an encodingmode according to maximum coding units are extracted from the parsedbitstream. The coded depth of each maximum coding unit is a depth havingthe least encoding error in each maximum coding unit. In encoding eachmaximum coding unit, the image data is encoded based on at least onedata unit obtained by hierarchically splitting each maximum coding unitaccording to depths.

According to the information about the coded depth and the encodingmode, the maximum coding unit may be split into coding units having atree structure. Each of the coding units having the tree structure isdetermined as a coding unit corresponding to a coded depth, and isoptimally encoded as to output the least encoding error. Accordingly,encoding and decoding efficiency of an image may be improved by decodingeach piece of encoded image data in the coding units after determiningat least one coded depth according to coding units.

In operation 1330, the image data of each maximum coding unit is decodedbased on the information about the coded depth and the encoding modeaccording to the maximum coding units. The decoded image data may bereproduced by a reproducing apparatus, stored in a storage medium, ortransmitted through a network.

Hereinafter, video encoding and decoding considering independent parsingor independent decoding in a coding unit level, according to exemplaryembodiments of the present invention will be described with reference toFIGS. 16 through 30.

FIG. 16 is a block diagram of a video encoding apparatus 1400 forindependent parsing and independent decoding in a coding unit level,according to an exemplary embodiment. Referring to FIG. 16, the videoencoding apparatus 1400 includes a maximum coding unit splitter 1410, acoding unit determiner 1420, and an output unit 1430.

The maximum coding unit splitter 1410 splits a current picture into atleast one maximum coding unit. Pixel value data of the maximum codingunit is output to the coding unit determiner 1420.

The coding unit determiner 1420 compresses and encodes the pixel valuedata of the maximum coding unit generated by the maximum coding unitsplitter 1410. In detail, the coding unit determiner 1420 encodes deepercoding units in split regions that are obtained by hierarchicallysplitting the maximum coding unit according to depths. Each split regionof the maximum coding unit is encoded at a current depth, and as a depthdeepens, each split region is split again to generate new split regions.Accordingly, a process of encoding corresponding deeper coding units inthe newly generated split region is recursively performed.

Encoding results obtained through a process recursively encoding deepercoding units in each split region of the maximum coding unit arecompared, and a depth having a highest encoding efficiency is determinedas an encoding depth of the corresponding split region. Since the depthshaving the highest encoding efficiency in split regions areindependently determined from each other, at least one encoding depthmay be determined in one maximum coding unit.

The coding unit determiner 1420 may perform parallel encoding on codingunits per a predetermined number of coding units in a slice level. Forexample, B slices that refer to a same I or P slice are encoded inparallel per a predetermined number of coding units.

The coding unit determiner 1420 may perform independent encoding in acoding unit level. Accordingly, information about an adjacent codingunit may not be referred to so as to encode a current coding unit.

Since the coding unit determiner 1420 performs independent encoding inthe coding unit level, the parallel encoding is performed on the codingunits per the predetermined number of coding units. Coding units to beencoded at a next cycle according to the parallel encoding in the codingunit level may not be used as reference information to encode codingunits to be encoded at a current cycle. Also, coding units to be encodedat the same cycle according to the parallel encoding in the coding unitlevel may not be used as reference information for each other.

A coding tool based on sequential encoding performs prediction encodingby referring to nearby information that is previously encoded accordingto a sequential order.

Accordingly, it may not be possible to use a coding tool based on thesequential encoding of coding units as it is, if the independentencoding is performed in the coding unit level. When the coding unitdeterminer 1420 independently performs intra prediction in the codingunit level, nearby information that may be referenced from among nearbyinformation that is encoded before the coding unit may be searched forand referred to, if the reference information of a current coding unitis not about a previous coding unit encoded before the current codingunit. A method of referring to the nearby information that may bereferenced from among the nearby information that is encoded before thecoding unit, wherein the method is performed for the coding tool, willnow be described.

When the coding unit determiner 1420 independently performs the intraprediction in the coding unit level, a direct current (DC) valueobtained by using information encoded before the current coding unitfrom among nearby information of the current coding unit may bedetermined as a prediction value of the current coding unit, if thereference information of the current coding unit is not about theprevious coding unit encoded before the current coding unit.

An intra prediction mode indicates a direction of nearby informationthat is referred to for intra prediction of the current coding unit.Accordingly, a plurality of intra prediction modes may be set based on anumber of directions of nearby information that may be referenced by thecurrent coding unit. When the coding unit determiner 1420 independentlyperforms the intra prediction in the coding unit level, only an intraprediction mode indicating an intra prediction direction about theinformation encoded before the current coding unit from among the nearbyinformation of the current coding unit may be compressed as a type ofthe intra prediction mode, if the reference information of the currentcoding unit is not about the previous coding unit encoded before thecurrent coding unit.

The coding unit determiner 1420 may perform frequency domain prediction,which predicts a transformation coefficient of the current coding unit,by using a transformation coefficient of the adjacent coding unit in afrequency domain. When the coding unit determiner 1420 independentlyperforms the frequency domain prediction in the coding unit level, thetransformation coefficient of the current coding unit may be predictedby using the information encoded before the current coding unit fromamong the nearby information of the current coding unit.

A frequency domain prediction mode according to an exemplary embodimentmay indicate a direction of the nearby information that is referred toby the current coding unit. When the coding unit determiner 1420independently performs the frequency domain prediction in the codingunit level, a frequency domain prediction mode of the current codingunit may be changed to a prediction mode indicating a direction of theinformation encoded before the current coding unit from among the nearbyinformation of the current coding unit, if the reference information ofthe current coding unit is not about the previous coding unit encodedbefore the current coding unit.

The coding unit determiner 1420 may search for information about areference possibility of the adjacent coding unit so as to search forthe reference information of the current coding unit for interprediction. When the coding unit determiner 1420 independently performsinter prediction in the coding unit level, a motion vector between theadjacent coding unit and the current coding unit may be predicted basedon a changed reference possibility from among the referencepossibilities of the nearby information of the current coding unit, ifthe reference information of the current coding unit is not about theprevious coding unit encoded before the current coding unit.

The coding unit determiner 1420 may perform a predetermined post processon a prediction value of the current coding unit, which is obtained byperforming the intra prediction on the current coding unit. The codingunit determiner 1420 may revise the prediction value of the currentcoding unit by using various parameters and the nearby informationaccording to a purpose of the post process. When the coding unitdeterminer 1420 independently performs the post process in the codingunit level after the intra prediction, a post processed pixel value ofthe current coding unit may be calculated by using a pixel value of thecurrent coding unit and a post processed pixel value of the adjacentpixel value in encoded nearby information of the current coding unit, ifthe reference information of the current coding unit is not about theprevious coding unit encoded before the current coding unit.

The coding unit determiner 1420 may perform entropy encoding accordingto context-based adaptive binary arithmetic coding (CABAC) using contextinformation of nearby information of a coding unit. When the coding unitdeterminer 1420 independently performs the entropy encoding in thecoding unit level, context information of the nearby information encodedbefore the current coding unit from among the nearby information of thecurrent coding unit may not be referred to in some cases.

The output unit 1430 outputs a bitstream including video data encoded inthe encoding depth determined for each maximum coding unit, andinformation about a coded depth and an encoding mode according to themaximum coding units. Also, the output unit 1430 inserts at least one ofinformation indicating independent parsing of a data unit andinformation indicating independent decoding of a data unit into thebitstream for independent parsing or independent decoding in the codingunit level.

The information indicating independent decoding of the data unit may beset based on whether the data units are independently encoded, and theinformation indicating independent parsing of the data unit may be setbased on whether the data units are independently inserted into thebitstream.

The data unit independently encoded may be a group of at least onecoding unit or a group of at least one maximum coding unit. Regardingthe data unit independently encoded, information indicating at least oneof a size of the coding unit, the number of the group of at least onecoding unit and the number of the group of at least one maximum codingunit may be encoded and inserted into the bitstream independently fromother data unit.

Independent parsing and independent decoding of the data unit accordingto exemplary embodiments may respectively include independent parsingand independent decoding in a slice level, or independent parsing andindependent decoding in a coding unit level. Accordingly, theinformation indicating independent parsing of the data unit may includeat least one of information indicating independent parsing in the slicelevel and information indicating independent parsing in the coding unitlevel, and the information indicating independent decoding of the dataunit may include at least one of information indicating independentdecoding in the slice level and information indicating independentdecoding in the coding unit level.

The information indicating independent parsing of the data unit and theinformation indicating independent decoding of the data unit may beindependently set from each other. Accordingly, a combination of theinformation indicating independent parsing of the data unit and theinformation indicating independent decoding of the data unit may be(true, false), (false, true), (true, true), or (false, false) based onwhether independent parsing or independent decoding is performed duringencoding.

The information indicating independent parsing of the data unit or theinformation indicating independent decoding of the data unit may bestored in a slice header or a sequence parameter set.

The output unit 1430 may insert information indicating whether toperform partial region decoding independently from other than data unitof the partial region or information indicating the target data unit ofthe partial region decoding into the bitstream.

The video encoding apparatus 1400 may independently encode a coding unitbased on nearby information. Since the video encoding apparatus 1400encodes data in a coding unit having a size of, for example, 32×32,64×64, 128×128, 256×256, or the like, which is larger than a related artmacroblock having a size of 8×8 or 16×16, the video encoding apparatus1400 may perform prediction encoding on a current coding unit by usingdata included in one coding unit. Accordingly, the video encodingapparatus 1400 is capable of performing independent encoding in thecoding unit level, wherein the prediction encoding is independentlyperformed on each coding unit.

Also, if a plurality of arithmetic processors capable of performingindependent encoding on coding units exist, a plurality of coding unitsmay be encoded in parallel. Accordingly, via the independent encoding inthe coding unit level, a decoder may perform independent parsing orindependent decoding on the coding units, and may perform parallelparsing and parallel decoding on the coding units.

FIG. 17 is a block diagram of a video decoding apparatus 1500 accordingto independent parsing and independent decoding in a coding unit level,according to an exemplary embodiment. Referring to FIG. 17, the videodecoding apparatus 1500 includes a receiver 1510, a parser 1520, and adecoder 1530. The receiver 1510 receives a bitstream of an encodedvideo. The receiver 1510 extracts at least one of information indicatingindependent parsing of a data unit and information indicatingindependent decoding of a data unit from the received bitstream.

The information indicating independent parsing of the data unit and theinformation indicating independent decoding of the data unit areseparately set from each other, and thus may be separately extracted.The information indicating independent parsing of the data unit and theinformation indicating independent decoding of the data unit may beextracted from a slice header of the bitstream or a sequence parameterset.

Performing of independent parsing or independent encoding may be definedin a slice level or a coding unit level. For example, the informationindicating independent parsing of the data unit and the informationindicating independent decoding of the data unit may respectivelyinclude information indicating independent parsing in a slice level andinformation indicating independent decoding in a slice level, orinformation indicating independent parsing in a coding unit level andinformation indicating independent decoding in a coding unit level.

Due to characteristics of an I slice, a P slice, and a B slice, the Islice may refer to nearby information to perform intra prediction on acurrent coding unit in some cases, and the P and B slices may not referto the nearby information for intra prediction in some cases.Accordingly, performance of the independent parsing or the independentdecoding in the slice level may be higher when used in the P and Bslices than when used in the I slice.

The parser 1520 extracts encoded information by parsing the bitstreamaccording to data units based on the information indicating independentparsing of the data unit. For example, if a bitstream about a video thatis encoded considering parsing in a coding unit level is received, theparser 1520 parses each maximum coding unit and extracts encoded videodata, information about a coded depth, and information about an encodingmode of a corresponding maximum coding unit.

The data unit, which is parsing or decoding independently from otherdata units, may be a group of at least one coding unit or a group of atleast one maximum coding unit. Regarding the data unit of independentparsing or decoding, information indicating at least one of a size ofthe coding unit, the number of the group of at least one coding unit orthe number of the group of at least one maximum coding unit may be alsoindependently parsed and extracted from the bitstream.

The decoder 1530 may independently decode the encoded video data of eachcoding unit, which is parsed and extracted by the parser 1520, based onthe information indicating independent decoding of the data unit, whichis extracted by the parser 1520. The encoded video data may be decodedin each coding unit corresponding to at least one encoding depth in themaximum coding unit, based on information about an encoding depth and anencoding mode of each coding unit corresponding to at least one encodingdepth, according to maximum coding units.

An arithmetic processor may perform independent parsing or independentdecoding according to data units. Accordingly, if there are a pluralityof arithmetic processors, the arithmetic processors may continuously andsimultaneously perform independent parsing and independent decoding ondifferent data units. Thus, a parallel process may be performed on aplurality of data units based on the independent parsing and independentdecoding according to the data units. A current data unit is decoded byreferring to only data units, which are parsed and decoded prior to thecurrent data unit according to the parallel process, among nearby dataunits.

A decoding tool based on sequential decoding decodes a current codingunit by referring to information about a previous coding unit that ispre-decoded according to a sequential order. Accordingly, the bitstreamreceived by the video decoding apparatus 1500 may include data that isindependently encoded according to data units, and thus it may not bepossible to restore original data by using the decoding tool based onsequential decoding of coding units as is.

If predetermined nearby information for performing prediction decodingon a coding unit may not be referenced since the predetermined nearbyinformation is not decoded before the current coding unit, the decoder1530 may perform prediction decoding on the current coding unit bysearching for and referring to nearby information that may be referencedby the current coding unit, according to the independent parsing orindependent decoding of the data unit.

When the decoder 1530 performs independent intra prediction in a codingunit level, a DC value calculated by using nearby information, which maybe currently referenced by the current coding unit, other than currentnearby information may be determined as a prediction value of thecurrent coding unit, if the current nearby information for performingintra prediction on the current coding unit may not be referenced.

Alternatively, when the decoder 1530 performs the independent intraprediction in the coding unit level, intra prediction may be performedin an intra prediction direction mode that is compressed only in anintra prediction direction of the nearby information, which may becurrently referenced by the current coding unit, other than currentnearby information, if the current nearby information for performingintra prediction on the current coding unit may not be referenced.

Thus, if the current data unit is independently parsed or decoded basedon the information indicating independent parsing of the data unit orthe information indicating independent decoding of the data unit,current nearby information is limited by the independent parsing anddecoding of the current data unit. Data units other than the currentnearby information may be not referred for performing inter(intra)prediction/compensation on the current data unit. When the decoder 1530performs independent frequency domain prediction in the coding unitlevel, a transformation coefficient of the current coding unit may berestored by using an adjacent coding unit, which may be currentlyreferenced by the current coding unit, other than current nearbyinformation, if the current nearby information for performing frequencydomain prediction on the current coding unit may not be referenced.

Specifically, a frequency domain prediction mode of a coding unit inencoding information may indicate a direction of the current nearbyinformation to be referred to by the coding unit. Accordingly, if thecurrent nearby information of the coding unit may not be referenced, thedecoder 1530 may restore the transformation coefficient of the currentcoding unit according to the frequency domain prediction mode that ischanged to indicate a direction of the adjacent coding unit, which maybe currently referenced by the current coding unit, other than thecurrent nearby information.

When the decoder 1530 performs independent inter prediction in thecoding unit level and reference possibilities of adjacent coding unitsfor performing inter prediction on the current coding unit are changed,a motion vector about an adjacent coding unit that is accessible basedon the changed reference possibilities may be used for inter predictionon the current coding unit.

When current nearby information of the current coding unit forperforming a post process after the independent intra prediction in thecoding unit level is not restored before the current coding unit, thedecoder 1530 may perform the post process on an intra prediction valueof the current coding unit by using a restored pixel value that may becurrently referenced from among adjacent restored pixel values of thecurrent coding unit, other than the current nearby information.

When the decoder 1530 performs independent entropy decoding according toCABAC in the coding unit level, context information of an adjacentcoding unit may not be referenced by the current coding unit, if thecurrent nearby information of the current coding unit may not bereferenced.

Since the decoder 1530 independently decodes the coding units, thedecoder 1530 is able to decode only at least one maximum coding unitcorresponding to a partial region of the encoded video data.Accordingly, only a partial area of an encoded video may be selectivelydecoded. If the parser 1520 extract information indicating whether toperform partial region decoding or information indicating target dataunit of the partial region decoding from the bitstream, the decoder 1530may determine whether to perform partial region decoding according toinformation indicating whether to perform partial region decoding, andperform decoding on data unit of the partial region corresponding toinformation indicating target data unit of the partial region decoding,independently from other than coding units of the partial region. Forexample, information indicating target data unit of the partial regiondecoding may include at least one of index of a maximum coding unit or acoding unit to be partially decoded and a range of maximum coding unitsor coding units to be partially decoded.

Also, since the decoder 1530 independently decodes the coding units inparallel, video data that is decoded in parallel in a coding unit levelmay be restored and reproduced in parallel in a maximum coding unitlevel. Time may be delayed when a display device reproduces pixels of alarge-scale coding unit. Furthermore, when the display devicesequentially reproduces coding units, time may be delayed to aconsiderable extent for a picture to be reproduced. Accordingly, whenthe display device processes and reproduces video data independently incoding units, which are decoded and restored in parallel in the codingunit level by the video decoding apparatus 1500, in parallel,reproduction time delay in the display device may be reduced.

Since the video decoding apparatus 1500 decodes data in a large codingunit, various types of image information may be included in one codingunit. Accordingly, the video encoding apparatus 1400 and the videodecoding apparatus 1500 according to exemplary embodiments may performencoding and decoding to reduce temporally or spatially overlapping dataof the coding unit by making use of information about one coding unitindependently from other coding units. Accordingly, the video encodingapparatus 1400 and the video decoding apparatus 1500 respectivelyperforms encoding and decoding independently according to coding unitsin the coding unit level.

FIG. 18 is an outline for describing a parallel process in a slice levelaccording to a H.264 standard encoding and decoding method.

The H.264 standard encoding and decoding method supports parallelprocess in a frame or slice level. Referring to FIG. 18, an I slice 1610is decoded without referring to another slice. Since a P slice 1620refers to the I slice 1610, the P slice 1620 is decoded after the Islice 1610. Since a B slice 1630 refers to the I and P slices 1610 and1620, the B slice 1630 is decoded after the I and P slices 1610 and1620.

Since a B slice 1640 refers to the I and B slices 1610 and 1630, the Bslice 1640 is decoded after the I and B slices 1610 and 1630, and sincea B slice 1650 refers to the P and B slices 1620 and 1630, the B slice1650 is decoded after the P and B slices 1620 and 1630. The B slices1640 and 1650, which do not refer to each other, may be processed inparallel. Since such B slices 1640 and 1650 that are processed inparallel do not have slice dependence, the B slices 1640 and 1650 may beprocessed regardless of a slice processing order.

FIG. 19 is a table showing possible combinations of a parallel processin a slice level, and a parallel process in a coding unit levelaccording to one or more exemplary embodiments.

A video encoding apparatus 1400 and a video decoding apparatus 1500according to exemplary embodiments may perform a hierarchical parallelprocess to a data unit in a level smaller than a slice level. Also,independent parsing and independent decoding for the parallel processmay be separately set. Similarly, parallel parsing and parallel decodingaccording to coding units may be separately set.

Referring to the table of FIG. 19, the hierarchical parallel process maynot only employ Case 1, wherein a parallel process is possible only to aslice level as in the H.264 standard encoding and decoding method, butmay also selectively combine parallel parsing in a coding unit level orparallel decoding in a coding unit level as shown in Case 2 and Case 3.Although not shown in FIG. 19, the video encoding apparatus 1400 and thevideo decoding apparatus 1500 may realize a case where all of theparallel process in the slice level, the parallel parsing in the codingunit, and the parallel decoding in the coding unit are employed.

Also, the video decoding apparatus 1500 may also selectively performparallel parsing and parallel decoding in the coding unit withoutperforming the parallel process in the slice level, as in Case 4 or Case5.

Parsing is an operation for reading a symbol in a bitstream and decodingis an operation of generating a restoration sample. Accordingly,arithmetic operations and throughputs of the decoding is more than thoseof the parsing, in the coding unit level. Accordingly, consideringperformance improvement in terms of throughput through the parallelprocess, Case 3 may be employed where sequential parsing and paralleldecoding are performed.

Also, if quality deterioration of a predicted image is of concern due toindependent decoding in the coding unit level, Case 1 or Case 2 may beemployed where parallel parsing and sequential decoding are performed inthe coding unit level.

Accordingly, the video encoding apparatus 1400 may selectively performthe independent encoding and the parallel encoding of the coding unitswhile considering at least one of hardware performance for encoding anddecoding, user's requirements, transmission environment, etc. Also, thevideo decoding apparatus 1500 may perform independent parsing orindependent decoding and parallel parsing or parallel decoding onencoded video data based on whether independent encoding or parallelencoding is performed on the encoded video data.

FIG. 20 is a diagram for describing a parallel process in a coding unitlevel, according to an exemplary embodiment. Referring to FIG. 20, avideo encoding apparatus 1400 and a video decoding apparatus 1500according to exemplary embodiments may divide a picture 1800 intomaximum coding units, and independently process the maximum coding unitsaccording to coding units. The video encoding apparatus 1400 mayindependently encode the maximum coding units in a coding unit level, ormay simultaneously encode a predetermined number of maximum coding unitsin parallel. For example, three maximum coding units 1810 through 1830may be simultaneously encoded at one cycle according to the parallelencoding.

Upon receiving a bitstream that is independently encoded in a codingunit level, the video decoding apparatus 1500 independently parses ordecodes coding units. For example, when a bitstream that is encodedaccording to parallel encoding is to be decoded, parallel parsing orparallel decoding may be performed on data about the three maximumcoding units 1810 through 1830.

FIG. 21 is a diagram for describing a hierarchical parallel process in adata unit, according to an exemplary embodiment.

A video encoding apparatus 1400 according to an exemplary embodiment mayindividually set parallel processes in a coding unit level according toslices. For example, referring to FIG. 21, since an I slice 1910, a Pslice 1920, and a B slice 1930 are to be referred to by each other, theI, P, and B slices 1910, 1920, and 1930 are not processed in parallel.Also, since B slices 1940 and 1950 are not referred to by each other,the B slices 1940 and 1950 are not processed in parallel. Accordingly,the I slice 1910 is decoded first, the P slice 1920 is decoded second,the B slice 1930 is decoded third, and the B slices 1940 and 1950 aredecoded fourth in relation to each other.

Also, even when the parallel process is performed in the slice level, asequential process or a parallel process may be selectively performed ina coding unit level according to the hierarchical parallel process. Forexample, sequential parsing and sequential decoding may be performed onthe I and P slices 1910 and 1920 in the coding unit level, and parallelparsing and parallel decoding may be performed on the B slices 1930through 1950 in the coding unit level.

Also, as described above, the parallel parsing and the parallel decodingmay be separately set in the coding unit level. That is, a combinationof parallel parsing and sequential decoding or a combination ofsequential parsing and parallel decoding may be selected in the codingunit level for a slice.

FIG. 22 is a diagram for describing possible partial decoding accordingto independent decoding in a coding unit level, according to anexemplary embodiment.

Referring to FIG. 22, a video encoding apparatus 1400 according to anexemplary embodiment independently encodes video data 2010 in a codingunit level. A video decoding apparatus 1500 according to an exemplaryembodiment receives a bitstream that is independently encoded in acoding unit, and restores the video data 2010 by independently parsingor decoding the bitstream in a coding unit level.

Accordingly, if the video decoding apparatus 1500 is to decode only apartial region 2015 of the video data 2010, maximum coding unitscorresponding to the partial region 2015 may be independently decodedand restored. Accordingly, a result image 2020 restored by the videodecoding apparatus 1500 may include a partially restored partial region2025.

FIG. 23 is a diagram of a possible parallel display in a coding unitaccording to parallel decoding in a coding unit level, according to anexemplary embodiment.

Video data encoded in a coding unit level by a video encoding apparatus1400 according to an exemplary embodiment may be decoded in parallel pera predetermined number of coding units by a video decoding apparatus1500 according to an exemplary embodiment. A display device receivesvideo signals of the coding units decoded and restored in parallel, andreproduce the coding units in parallel.

For example, referring to FIG. 23, the video decoding apparatus 1500independently decodes and restores a picture 2100 including maximumcoding units A1 through A4, B1 through B4, C1 through C4, D1 through D4,and E1 through E4 in a coding unit level.

The video decoding apparatus 1500 according to the present exemplaryembodiment may decode and restore five consecutive maximum coding unitsin a horizontal direction, in parallel. A group 2110 of the maximumcoding units A1 through E1 may be decoded and restored at a firstprocessing cycle, a group 2120 of the maximum coding units A2 through E2may be decoded and restored at a second processing cycle, a group 2130of the maximum coding units A3 through E3 may be decoded and restored ata third processing cycle, and a group 2140 of the maximum coding unitsA4 through E4 may be decoded and restored at a fourth processing cycle.Here, in order to reproduce the picture 2100, a display device mayreproduce the restored maximum coding units A1 through A4, B1 throughB4, C1 through C4, D1 through D4, and E1 through E4 in the restoredorder in parallel per the five consecutive maximum coding units.

Alternatively, in another exemplary embodiment, the video decodingapparatus 1500 may decode and restore four consecutive maximum codingunits in a vertical direction, in parallel. In this case, a group of themaximum coding units A1 through A4 may be decoded and restored at afirst processing cycle, a group of the maximum coding units B1 throughB4 may be decoded and restored at a second processing cycle, a group ofthe maximum coding units C1 through C4 may be decoded and restored at athird processing cycle, a group of the maximum coding units D1 throughD4 may be decoded and restored at a fourth processing cycle, and a groupof the maximum coding units E1 through E4 may be decoded and restored ata fifth processing cycle. Here, in order to reproduce the picture 2100,the display device may reproduce the restored maximum coding units A1through A4, B1 through B4, C1 through C4, D1 through D4, and E1 throughE4 in the restored order in parallel per the four consecutive maximumcoding units.

FIG. 24 is a syntax of a sequence parameter set 2200 into whichinformation indicating independent parsing in a coding unit level andinformation indicating independent decoding in a coding unit level areinserted, according to an exemplary embodiment. A sequence parameter setas used herein denotes the syntax of the sequence parameter set 2200about a current image slice. In FIG. 24, the information indicatingindependent parsing in the coding unit level and the informationindicating independent decoding in the coding unit level are insertedinto the syntax of the sequence parameter set 2200 about the currentimage slice.

Furthermore, in FIG. 24, picture_width indicates a height of an inputimage, max_coding_unit_size indicates a size of a maximum coding unit,and max_coding_unit_depth denotes a maximum depth.

Information (i.e., use_independent_cu_decode_flag) indicatingindependent decoding in a coding unit level, information (i.e.,use_independent_cu_parse_flag) indicating independent parsing in acoding unit level, information (i.e., use_my_accuracy_control_flag)indicating availability of a control operation on motion vectoraccuracy, information (i.e., use_arbitrary_direction_intra_flag)indicating availability of an intra prediction operation in arbitrarydirectionality, information (i.e., use_frequency_domain_prediction_flag)indicating availability of a prediction encoding and decoding operationfor frequency transformation, information (i.e.,use_rotational_transform_flag) indicating availability of a rotationaltransformation operation, information (i.e.,use_tree_significant_map_flag) indicating availability of encoding anddecoding using a tree significant map, information (i.e.,use_multi_parameter_intra_prediction_flag) indicating availability of anintra prediction encoding operation using a multi parameter, information(i.e., use_advanced_motion_vector_prediction_flag) indicatingavailability of an improved motion vector prediction encoding operation,information (i.e., use_adaptive_loop_filter_flag) indicatingavailability of an adaptive loop filtering operation, information (i.e.,use_quadtree_adaptive_loop_filter_flag) indicating availability of anadaptive loop filtering operation in a quadtree structure, information(i.e., use_delta_qp_flag) indicating availability of a quantizationoperation using a deta value of a quantization parameter, information(i.e., use_random_noise_generation_flag) indicating availability of arandom noise generation operation, and information (i.e.,use_arbitrary_motion_partition_flag) indicating availability of a motionprediction operation according to a prediction unit that is split inarbitrary shaped partitions may be defined as examples of a sequenceparameter. The syntaxes indicating availability of various operationsenable effective encoding and decoding by defining whether acorresponding operation is used while encoding and decoding a currentslice.

Specifically, a filter length (i.e., alf_filter_length) of an adaptiveloop filter, a type (i.e., alf_filter_type) of the adaptive loop filter,a reference value Q bits (i.e., alf_qbits) for quantizing a coefficientof the adaptive loop filter, and a number (i.e., alf_num_color) of colorcomponents in the adaptive loop filter may be defined in the sequenceparameter set 2200 according to the use_adaptive_loop_filter_flag andthe use_quadtree_adaptive_loop_filter_flag.

Information about a correspondence relationship between a depth of acoding unit, a coding tool, and an operation mode, which is used by avideo encoding apparatus 1400 and a video decoding apparatus 1500according to exemplary embodiments, may include an operation mode (i.e.,mvp_mode[uiDepth]) of inter prediction corresponding to a depth (i.e.,uiDepth) of a coding unit, and an operation mode (i.e.,significant_map_mode[uiDepth]) indicating a type of a significant mapfrom among the tree significant map. That is, a correspondencerelationship between inter prediction and a corresponding operation modeor between encoding and decoding using the tree significant map and acorresponding operation mode, according to the depth of the coding unit,may be set in the sequence parameter set 2200.

A bit depth of an input sample (i.e., input_sample_bit_depth) and a bitdepth of an internal sample (i.e., internal_sample_bit_depth) may alsobe set in the sequence parameter set 2200.

The video decoding apparatus 1500 may extract theuse_independent_cu_decode_flag and the use_independent_cu_parse_flag byreading the sequence parameter set 2200, and determine whether toperform independent parsing or independent decoding in the coding unitlevel in a corresponding sequence.

The use_independent_cu_decode_flag and theuse_independent_cu_parse_flag, which are set, encoded, and decoded bythe video encoding apparatus 1400 and the video decoding apparatus 1500,may be inserted into the sequence parameter set 2200 of FIG. 24 and mayalso be set, encoded, and decoded in a unit of slices, frames, pictures,or GOPs.

When the use_independent_cu_parse_flag is included in a slice header,independent parsing may be performed in the coding unit level in acorresponding slice if the use_independent_cu_parse_flag is “true,” andrelated sequential parsing may be performed in the corresponding sliceif the use_independent_cu_parse_flag is “false.”

Also, when the use_independent_cu_decode_flag is included in the sliceheader, independent decoding may be performed in the coding unit levelin a corresponding slice if the use_independent_cu_decode_flag is“true,” and related art sequential decoding may be performed in thecorresponding slice if use_independent_cu_decode_flag is “false.”

FIG. 25 is a diagram for describing intra prediction for independentdecoding in a coding unit level, according to an exemplary embodiment.

Referring to FIG. 25, a video decoding apparatus 1500 according to anexemplary embodiment may perform intra prediction in an arbitrarydirection on a current coding unit 2310 while considering directions ofadjacent coding units 2320, 2330, and 2340 with respect to the currentcoding unit. The intra prediction in the arbitrary direction calculatesan intra prediction value of the current coding unit 2310 according toextrapolation that uses restoration samples of the adjacent coding units2320, 2330, and 2340 of the current coding unit 2310.

According to independent decoding in a coding unit level, therestoration samples of the adjacent coding units 2330 and 2340respectively disposed on boundaries 2335 and 2345 of the current codingunit 2310 may not be referenced. If pixel values on the boundary 2335between the current coding unit 2310 and the adjacent coding unit 2330above the current coding unit 2310 may not be referenced because theadjacent coding unit 2330 is not yet decoded, only intra prediction maybe performed by referring to pixel values on the boundary 2345 betweenthe current coding unit 2310 and the adjacent coding unit 2340 on theleft of the current coding unit 2310. For example, a DC value of thepixel values on the boundary 2345 may be calculated as an intraprediction value of the current coding unit 2310.

Similarly, if the pixel values on the boundary 2345 between the currentcoding unit 2310 and the adjacent coding unit 2340 may not be referencedbecause the adjacent coding unit 2340 is not yet decoded, intraprediction may be performed by referring to the pixel values on theboundary 2335 between the current coding unit 2310 and the adjacentcoding unit 2330. For example, a DC value of the pixel values on theboundary 2335 may be calculated as the intra prediction value of thecurrent coding unit 2310.

Also, if both of the adjacent coding units 2330 and 2340 may not bereferenced because the adjacent coding units 2330 and 2340 are not yetdecoded, a predetermined DC value may be selected as the intraprediction value of the current coding unit 2310 or an intra predictionmode of the current coding unit 2310 may be set as an impossibleprediction mode.

Alternatively, a video encoding apparatus 1400 according to an exemplaryembodiment may independently perform the intra prediction in arbitrarydirectionality on the current coding unit 2310 without referring to theadjacent coding units 2320, 2330, and 2340 of the current coding unit2310.

The video encoding apparatus 1400 may perform frequency domainprediction. According to the frequency domain prediction, a predictionvalue of a transformation coefficient of a current coding unit in afrequency domain may be calculated by using restoration samples ofadjacent coding units. Accordingly, the video decoding apparatus 1500 isable to perform prediction decoding in the frequency domain. Thetransformation coefficient of the current coding unit in the frequencydomain may be restored by using the restoration samples of the adjacentcoding units.

A frequency domain prediction mode is defined according to a directionof nearby information being referred to. For example, when nearbyinformation in a vertical direction is referred to, the frequency domainprediction mode (i.e., FDP_mode) is set to 0 (i.e., FDP_mode=0), andwhen nearby information in a horizontal direction is referred to, thefrequency domain prediction mode is set to 1 (i.e., FDP_mode=1). Also,by way of example, in a coding unit complying with a DC intra predictionmode, the frequency domain prediction mode is set to 2 (i.e.,FDP_mode=2), and when both of the nearby information in the verticaldirection and the horizontal direction is referred to, the frequencydomain prediction mode is set to 3 (i.e., FDP_mode=3).

In order for the video encoding apparatus 1400 to restore thetransformation coefficient of the current coding unit by using nearbyinformation, a restoration sample of a previous coding unit that isdecoded before the current coding unit is referred to. However, ifreference information used to restore the transformation coefficient ofthe current coding unit is a sample that may not be referenced accordingto independent encoding in a coding unit level, the video decodingapparatus 1500 may use an accessible restoration sample from among thenearby information.

For example, if a transformation coefficient of an independent uppercoding unit may not currently be referenced according to independentencoding in a coding unit level, the video encoding apparatus 1400changes a frequency domain prediction mode to FDP_mode=1 that refers tonearby information in a horizontal direction so as to refer toinformation about a left coding unit. Similarly, if a transformationcoefficient of the left coding unit may not currently be referenced, thevideo encoding apparatus 1400 changes the frequency domain predictionmode to FDP_mode=0 that refers to nearby information in a verticaldirection so as to refer to the transformation coefficient of the uppercoding unit.

However, if the current coding unit is a maximum coding unit, thefrequency domain prediction is not performed.

If the use_independent_cu_decode_flag or theuse_independent_cu_parse_flag is determined to be “true,” andindependent parsing or independent decoding is employed in a coding unitlevel, the video decoding apparatus 1500 may perform decoding accordingto independent frequency domain prediction in the coding unit level.However, current nearby information may be unable to be referred toaccording to independent parsing or independent decoding in the codingunit level.

Encoding information that is inserted into a bitstream and transmittedby the video encoding apparatus 1400 may include a frequency domainprediction mode (i.e., FDP_mode) that is adjusted to indicate nearbyinformation that may be referenced for frequency domain predictionindependently performed in the coding unit level. Accordingly, the videodecoding apparatus 1500 may extract the encoding information from thebitstream and perform frequency domain prediction decoding independentlyin the coding unit level according to a frequency domain prediction modein the encoding information.

FIG. 26 is a diagram for describing a post process of intra predictionusing a nearby restoration sample, according to an exemplary embodiment.

When independent encoding in a coding unit level is not considered, avideo encoding apparatus 1400 according to an exemplary embodiment mayperform multi parameter intra prediction, which performs a post processon an intra prediction value of a current coding unit, by usingrestoration samples of adjacent coding units of the current coding unitas multi parameters.

Referring to FIG. 26, white circular pixels of a current coding unit2400 are samples of an intra prediction value, and black circular pixelsin an area 2405 around the current coding unit 2400 are nearbyrestoration samples. In operation S2411, an upper left pixel is postprocessed by using an upper nearby restoration sample and a left nearbyrestoration sample. A post processed restoration sample of the currentcoding unit 2400 is shown in a white square pixel.

As shown in operations S2412 through 2416, an intra prediction value ofa current pixel is post processed by using the upper or left nearbyrestoration samples (black circular pixels) of the current pixel or thepost processed restoration sample (white square pixel) of the currentcoding unit 2400.

FIG. 27 is a diagram for describing a post process of intra predictionfor independent decoding in a coding unit level, according to anexemplary embodiment.

When a video encoding apparatus 1400 according to an exemplaryembodiment performs independent encoding in a coding unit level,restoration samples of adjacent coding units of a current coding unitmay not be referenced, and thus a parameter for multi parameter intraprediction may be changed.

Referring to FIG. 27, white circular pixels of a current coding unit2450 are samples of an intra prediction value, and black circular pixelsin an area 2455 around the current coding unit 2450 are nearbyrestoration samples. Here, the nearby restoration samples in the area2455 may not be referenced according to independent encoding in a codingunit level.

Here, since an upper left pixel is unable to refer to an upper nearbyrestoration sample and a left nearby restoration sample, the videoencoding apparatus 1400 determines a current DC value as a post processvalue in operation S2461. Also, a right pixel and a lower pixel of thepost processed upper left pixel may be post processed by using the postprocessed upper left pixel and a lower pixel respectively below theright pixel and the lower pixel.

Similarly, as shown in operations S2462 through 2465, the intraprediction value of the current pixel may be post processed by usingpost processed restoration samples from among upper, left, and lowerpixels of the current pixel in the current coding unit 2450.

If a nearby restoration sample of a current coding unit may not bereferenced according to independent parsing or independent decoding in acoding unit level, a video decoding apparatus 1500 according to anexemplary embodiment may use post processed restoration samples fromamong upper, left, and lower pixels of a current pixel in the currentcoding unit so as to post process an intra prediction value of thecurrent coding unit.

FIG. 28 is a diagram for describing entropy encoding and decodingcomplying with a CABAC method, for independent decoding in a coding unitlevel according to an exemplary embodiment, and independent parsing in acoding unit level according to an exemplary embodiment.

In order to perform the entropy encoding complying with the CABACmethod, a video encoding apparatus 1400 according to an exemplaryembodiment may refer to pixels of a current coding unit, and pixels onboundaries between the current coding unit and an upper coding unit andbetween the current coding unit and a left coding unit.

When the independent decoding is performed in the coding unit level, thevideo encoding apparatus 1400 is unable to refer to restoration samplesof adjacent coding units of the current coding unit so as to perform theentropy encoding complying with the CABAC method.

For example, referring to FIG. 28, a boundary 2525 between an uppercoding unit (CUa) 2520 and a current coding unit (CUcurrent) 2510, and aboundary 2535 between a left coding unit Cub 2530 and the CUcurrent 2510may be referred to so as to perform entropy encoding on the CUcurrent2510 according to sequential encoding in the coding unit level.

However, pixels of the boundaries 2525 and 2535 may not be referred toperform the entropy encoding on the CUcurrent 2510 according to theindependent encoding in the coding unit level. Also, restoration sampleson the boundaries 2525 and 2535 may not be referenced to perform theentropy decoding on the CUcurrent 2510 even according to the entropydecoding in the coding unit level.

FIG. 29 is a flowchart illustrating a video encoding method forindependent parsing or independent decoding, according to an exemplaryembodiment. Referring to FIG. 29, in operation 2610, a current pictureis split into at least one maximum coding unit. In operation 2620, atleast one encoding depth and corresponding coding unit are determinedfor each of the at least one maximum coding unit by encoding at leastone split region generated as a depth deepens. According to the method,independent encoding in a coding unit level, which does not refer tonearby information to encode a current coding unit, is possible. Also,in an arithmetic environment that simultaneously supports a plurality ofarithmetic processors, the independent encoding, wherein each of codingunits are independently encoded based on nearby information, andparallel encoding, wherein a plurality of coding units aresimultaneously encoded in parallel, may be realized.

In operation 2630, a bitstream including encoded video data andinformation about a coded depth and an encoding mode according tomaximum coding units may be output for each maximum coding unit. Atleast one of information indicating independent parsing of a data unit,and information indicating independent decoding of a data unit may beinserted into the bitstream. Specifically, information indicatingwhether the independent parsing or independent encoding in the codingunit level is supported may be inserted into and output with thebitstream.

FIG. 30 is a flowchart illustrating a video decoding method according toindependent parsing or independent decoding, according to an exemplaryembodiment. Referring to FIG. 30, in operation 2710, a bitstream of anencoded video is received, and at least one of information indicatingindependent parsing of a data unit and information indicatingindependent decoding of the data unit is extracted from the bitstream.The information indicating independent parsing and independent decodingof the data unit may be extracted from a slice header, a sequenceparameter set, or information according to coding units.

Independent parsing or independent decoding of the data unit may beindependent parsing or independent decoding in a slice level or in acoding unit level.

In operation 2720, the bitstream is parsed based on the informationindicating independent parsing of the data unit, and video data encodedaccording to maximum coding units and encoding information are extractedfrom the bitstream. The encoding information may include informationabout at least one encoding depth in a corresponding maximum codingunit, and information about an encoding mode according to coding unitsof the at least one encoding depth. For example, if the informationindicating independent parsing of the data unit is “true,” a symbol of acurrent coding unit may be parsed without referring to nearbyinformation.

In operation 2730, a coding unit according to at least one coded depthis decoded according to maximum coding units of the encoded video data,based on the information indicating independent decoding of the dataunit, and information about a coded depth and an encoding mode accordingto maximum coding units. If the information indicating independentdecoding of the data unit defines independent decoding in a coding unitlevel, the encoded video data according to the maximum coding units maybe decoded without referring to information about adjacent coding units.

Nearby information that is referred to so as to decode a current codingunit by using a decoding tool using sequential decoding may not beaccessible according to independent decoding. Here, referenceinformation for the current coding unit may be changed so as to performprediction decoding on the current coding unit by referring to currentlyaccessible information.

According to an exemplary embodiment, since a large coding unit may beused, prediction encoding and decoding may be performed on a currentcoding unit without having to refer to nearby information. Also, adecoder using a plurality of arithmetic processors may be realized ashardware performance improves and hardware cost is decreased.Accordingly, parallel decoding may be performed in a coding unit levelas each of the arithmetic processors simultaneously perform independentparsing and independent decoding in the coding unit level on differentcoding units.

While not restricted thereto, one or more exemplary embodiments can bewritten as computer programs and can be implemented in general-usedigital computers that execute the programs using a computer readablerecording medium. Examples of the computer readable recording mediuminclude magnetic storage media (e.g., ROM, floppy disks, hard disks,etc.) and optical recording media (e.g., CD-ROMs, or DVDs). Moreover,while not required in all exemplary embodiments, one or more units ofthe video encoding apparatus 100 or 1400 and the video decodingapparatus 200 or 1500 can include a processor or microprocessorexecuting a computer program stored in a computer-readable medium.

While exemplary embodiments have been particularly shown and describedwith reference to the drawings, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinventive concept as defined by the appended claims. The exemplaryembodiments should be considered in descriptive sense only and not forpurposes of limitation. Therefore, the scope of the inventive concept isdefined not by the detailed description of the exemplary embodiments butby the appended claims, and all differences within the scope will beconstrued as being included in the present inventive concept.

1. A video decoding method comprising: extracting, from a bitstream ofencoded video data, at least one of information indicating independentparsing of a data unit, and information indicating independent decodingof a data unit, the data unit including one of a group of at least onecoding unit and a group of at least one maximum coding unit; extractingencoded video data, and information about a coded depth and an encodingmode according to maximum coding units, by parsing the bitstream basedon the information indicating independent parsing of the data unit; anddecoding at least one coding unit according to a coded depth of eachmaximum coding unit of the encoded video data, based on the informationindicating independent decoding of the data unit and the informationabout the coded depth and the encoding mode according to maximum codingunits.
 2. The video decoding method of claim 1, wherein: the informationindicating independent parsing of the data unit comprises informationindicating independent parsing in a coding unit level, which indicateswhether it is possible to extract information independently encoded foreach maximum coding unit from the bitstream; and the informationindicating independent decoding of the data unit comprises informationindicating independent decoding in a coding unit level, which indicateswhether it is possible to decode data independently encoded for eachmaximum coding unit.
 3. The video decoding method of claim 2, whereinthe information indicating independent parsing in the coding unit leveland the information indicating independent decoding in the coding unitlevel are set independently from each other.
 4. The video decodingmethod of claim 1, wherein the decoding comprises, if predeterminednearby information is not referenceable to perform prediction decodingon the at least one coding unit, performing prediction encoding on theat least one coding unit by searching for and referring to referenceablenearby information, according to the information indicating independentparsing of the data unit and the information indicating independentdecoding of the data unit.
 5. The video decoding method of claim 1,wherein the decoding comprises, if only a partial region of the encodedvideo is to be decoded, decoding only at least one maximum coding unitof the encoded video data, which corresponds to the partial region,based on the information indicating independent encoding in the codingunit level, wherein the extracting further extracts at least one ofinformation indicating whether to perform partial region decoding on thedata unit and information indicating target data unit of the partialregion decoding.
 6. The video decoding method of claim 1, furthercomprising restoring and reproducing video data, which is decoded inparallel per a predetermined number of coding units in the coding unitlevel, in parallel in the coding unit level, based on the informationindicating independent encoding in the coding unit level.
 7. The videodecoding method of claim 4, wherein the performing the predictiondecoding comprises, if current nearby information is not referenceableto perform intra prediction on the at least one coding unit, determininga prediction value of the at least one coding unit as a direct currentvalue by using currently referenceable nearby information by the atleast one coding unit.
 8. The video decoding method of claim 4, whereinthe performing the prediction decoding comprises, if current nearbyinformation is not referenceable to perform intra prediction on the atleast one coding unit, performing intra prediction on the at least onecoding unit according to an intra prediction direction mode that iscompressed only in an intra prediction direction, in which currentlyreferenceable nearby information is referred, by the at least one codingunit.
 9. The video decoding method of claim 4, wherein: the performingthe prediction decoding comprises restoring a transformation coefficientof the at least one coding unit by using a transformation coefficient ofan adjacent coding unit of the at least one coding unit so as to performfrequency domain prediction on the at least one coding unit; and therestoring the transformation coefficient comprises, if current nearbyinformation is not referenceable to perform the frequency domainprediction on the at least one coding unit, restoring the transformationcoefficient of the at least one coding unit by using a transformationcoefficient of another currently referenceable adjacent coding unit bythe at least one coding unit.
 10. The video decoding method of claim 2,further comprising performing parallel parsing in which coding units aresimultaneously parsed per a plurality of coding units, or paralleldecoding in which coding units are simultaneously decoded per aplurality of coding units, by using a plurality of independentprocessors.
 11. The video decoding method of claim 1, wherein deepercoding units of the maximum coding unit have a hierarchical structure,in which a coding unit of an upper depth is split as a depth deepens,according to at least one split region of the maximum coding unit, andan encoding depth of each of the at least one split region is a depth ofa coding unit to output an encoding result from among deeper codingunits in a corresponding split region, and the encoding depths of the atleast one split region in the maximum coding unit are independentlydetermined.
 12. The video decoding method of claim 1, wherein theextracting comprises extracting the information regarding the data unit,indicating at least one of a size of the coding unit, the number of thegroup of at least one coding unit and the number of the group of atleast one maximum coding unit.
 13. The video decoding method of claim 1,wherein the extracting comprises extracting the at least one of theinformation indicating independent parsing and the informationindicating independent decoding from a slice header or a sequenceparameter set.
 14. A video encoding method comprising: splitting acurrent picture into at least one maximum coding unit; determining anencoding depth and a coding unit corresponding to the encoding depth tooutput a result of encoding video data of the at least one maximumcoding unit based on deeper coding units having a hierarchicalstructure, in which a coding unit of an upper depth is split as a depthdeepens, according to at least one split region of the at least onemaximum coding unit; and outputting a bitstream comprising video dataencoded in the encoding depth for each of the at least one maximumcoding unit, information about a coded depth and an encoding modeaccording to the at least one maximum coding unit, and at least one ofinformation indicating independent parsing of a data unit andinformation indicating independent decoding of a data unit, wherein thedata unit including one of a group of at least one coding unit and agroup of at least one maximum coding unit.
 15. The video encoding methodof claim 14, wherein the outputting the bitstream comprises setting theinformation indicating independent decoding of the data unit based onwhether the data unit is independently encoded while encoding the videodata to determine the encoding depth.
 16. The video encoding method ofclaim 14, wherein the outputting the bitstream comprises setting theinformation indicating independent parsing of the data unit based onwhether the encoded video data and the information about the coded depthand the encoding mode according to at least one maximum coding unit areindependently inserted into the bitstream for each data unit.
 17. Thevideo encoding method of claim 14, wherein the information indicatingindependent parsing of the data unit comprises information indicatingindependent parsing in a coding unit level, and the informationindicating independent decoding of the data unit comprises informationindicating independent decoding in a coding unit level.
 18. The videoencoding method of claim 17, wherein the information indicatingindependent parsing in the coding unit level and the informationindicating independent decoding in the coding unit level areindependently set from each other.
 19. The video encoding method ofclaim 14, wherein the determining the encoding depth and the coding unitcomprises, if reference information used to perform prediction encodingon the coding unit is not information about a previous coding unit andthe coding unit is independently encoded in the coding unit level,searching for and referring to referenceable nearby information fromamong nearby information encoded before the coding unit so as to predictthe coding unit.
 20. The video encoding method of claim 14, wherein thedetermining the encoding depth and the coding unit comprises performingparallel encoding in which coding units are simultaneously decoded per aplurality of coding units by using a plurality of independentprocessors.
 21. The video encoding method of claim 14, furthercomprising hierarchically splitting a maximum coding unit as a depthdeepens and obtaining at least one split region in the maximum codingunit as deeper coding units; and independently determining encodingdepths of the at least one split region, wherein the encoding depth ofeach of the at least one split region is a depth of a coding unit tooutput an encoding result from among deeper coding units in acorresponding split region.
 22. The video encoding method of claim 21,wherein the outputting further outputs the information regarding thedata unit, indicating at least one of a size of the coding unit, thenumber of the group of at least one coding unit and the group of atleast one maximum coding unit.
 23. The video encoding method of claim14, wherein the outputting comprises outputting the bitstream comprisingthe at least one of the information indicating independent parsing andthe information indicating independent decoding in a slice header or asequence parameter set.
 24. A video decoding apparatus comprising: areceiver which extracts, from a bitstream of encoded video data, atleast one of information indicating independent parsing of a data unit,and information indicating independent decoding of a data unit, the dataunit including one of a group of at least one coding unit and a group ofat least one maximum coding unit; a parser which extracts encoded videodata, and information about a coded depth and an encoding mode accordingto maximum coding units, by parsing the bitstream based on theinformation indicating independent parsing of the data unit; and adecoder which decodes at least one coding unit according to a codeddepth of each maximum coding unit of the encoded video data, based onthe information indicating independent decoding of the data unit and theinformation about the coded depth and the encoding mode according tomaximum coding units.
 25. A video encoding apparatus comprising: amaximum coding unit splitter which splits a current picture into atleast one maximum coding unit; a coding unit determiner which determinesan encoding depth and a coding unit corresponding to the encoding depthto output a result of encoding video data of the at least one maximumcoding unit based on deeper coding units having a hierarchicalstructure, in which a coding unit of an upper depth is split as a depthdeepens, according to at least one split region of the at least onemaximum coding unit; and an output unit which outputs a bitstreamcomprising video data encoded in the encoding depth for each of the atleast one maximum coding unit, information about a coded depth and anencoding mode according to the at least one maximum coding unit, and atleast one of information indicating independent parsing of a data unitand information indicating independent decoding of a data unit, whereinthe data unit including one of a group of at least one coding unit and agroup of at least one maximum coding unit.
 26. A video decoding methodcomprising: extracting, from a bitstream, encoded video data andinformation about a coded depth and an encoding mode according tomaximum coding units by parsing the bitstream based on informationindicating independent parsing of a data unit; and decoding at least onecoding unit according to a coded depth of each maximum coding unit ofthe encoded video data, based on information indicating independentdecoding of a data unit and the information about the coded depth andthe encoding mode according to maximum coding units, wherein the dataunit including one of a group of at least one coding unit and a group ofat least one maximum coding unit.
 27. A computer readable recordingmedium having recorded thereon a program for executing the videodecoding method of claim
 1. 28. A computer readable recording mediumhaving recorded thereon a program for executing the video encodingmethod of claim
 14. 29. A computer readable recording medium havingrecorded thereon a program for executing the video encoding method ofclaim 26.